Where can I get software of this dinosaur on 21st century?
You can think that it's impossible, diferent disks and the CPC hasn't got a serial port, you are wrong: you can transfer your old 3" disks to newer 3 1/2" disk or CD-ROM (If you have a CD recorder). There are a lot of ways to run CPC software on a PC, there are the easiest:
Estos caminos también son válidos para pasar software del PC al Amstrad CPC para, por ejemplo, ejecutar juegos bajados de internet en su máquina nativa.
It's the easiest, no jacks, no heartdakes. You can be carefull with copyrights because there still are some CPC software which aren't shareware nor freeware. You must know where you are and especially what you distribuite, if you haven't permission you are pyracing.
I know a FTP where they care about this and have a lot of software: The Emmanuel Roussin's FTP: ftp://ftp.lip6.fr/pub/amstrad.
What is a FTP address? Could not I use my IE or Netscape and download those files?
In theory you could, but you might download each file one in one, they are small but too many (dozens of thousand).
I recomend you download in some days while you navigate for other Webs you're interested or look your e-mail, perhaps you have a message of an admirer.
F.T.P. means File Transfer Protocol. It's like a remote HD was another drive of your PC, this "drive" is in another place in the world (France at this case). If you can download the files select them drag & drop on a directory of your own HD, but it's "a bit slower" that copying disks.
What program I need? A client of FTP, although better I would recommend you a program whose main function is not this but compress and copy files and I also have the instructions, the Windows Commander, the best CN clone, compressor and client of FTP. It's the easiest and most quick one.
If you use Linux you have Midnight Commander, you don't need to install anything, just type 'mc'.
Hasn't anybody got a sound card? This is the surest and more simple method, you need only a tape unit and a cable with two jack in order to connect a source of audio to your sound card. Also it's the cheapest option, around a euro/dolar.
The big danger is that you connect a potent tape unit to your sound card in maximum powerfull, you probably break the card off. Use low volume and no problem.
You can record your CPC tapes like WAV files or in the sound format you need.
An emulator, the multi-machine, can read digitalized tapes in WAV format, but I don't like that a program of a few Ks comes to occupy several Mb, I don't thing it's a reasonable solution.
There are programs that are able to extract the files of a digitalized CPC tapes, so CPC programs will occupy what occupied in the CPC, or even less if you use ZIP compress. You can saving space, (between 7 or 20 CPC disk per PC disk); it is a good method in order to have all the files of a program in one only, you have all orderly
I know two programs to do this:
AIFF decoder v1.2 (extract CPC files from an AIFF file)
Voc2TZX: software for converting VOC Spectrum tape to TZX format but also runs with CPC tapes.
CPCAS v1.0 (extract CPC files from an PCM RAW 8bits Mono)
To digitalize CPC tape you can use Cool Edit, which supports these formats.
This would be the easiest method about the software used, but make the hardware require a little more of effort and of looking after, but it really are worthwhile!!!
Personally I have used this system in order to recover my old programs and, in fact, I am not an expert of welding or electronic (In fact I have not welded anything).
What did we need? In theory two connectors of printer, one for the PC and another for the CPC, and a cable of 7 threads and connect them according to the outline that comes in the manual of CPCEMU.
Unfortunately Nobody sells CPC printer conector for a decade, but to big wrongs, big remedies. Do you have seen the peg that is used in order to connect internal 5 1/ 4 disk drive to the PC? It's the same! But the numbers of the pines could be changed, so care and do not follow these numbers.
The best way is read the CPC and PC manuals about printer conections.
The outline of the connection is the following:

You are seeing these ports as you watch the back side of your computers.
What is necessary to buy? a cable of printer of PC and a cable in order to connect 5 1/ 4 internal disk drives (somebody maybe give it to you, because there is a lot of disk PC controllers broken off). Then simply makes a cut in the cables and unite the right threads into a wooden box .
The final result was this:

I recomend you use a connection checker, you can make one of them win a bulb and a battery:

If you want more information download the Marco Vieth emulator "CPCEMU", read the manual carefully before you begin the project and remember than pins may be changed .
This emulator works very well in MS-DOS, although in Windows 95 it is necessary to make you some tricks with the memory administration. It's the only one which can read CPC files without passing it into a DSK file (image of disk of 3"), but the most interesting thing is a complement software to transfer files using the Marco Vieth's parallel cable: PCPARA.
This application is able to pass files of the CPC to the PC and vice versa to a speed of very high rate.
There is other interesting program which is able to overturn a disk of 3" complete of a single passing, converting it in a DSK file that could be read on all CPC emulators: D.I.C.
4.- PLUG A 3.5" PC FLOPPY DISC TO CPC:
This way is a bit complicated but CPC floppy controller is similar than PC ones (only some details due to Amstrad wants some incompatibility, of course). Also it's a bit more expensive.

See Diego A. Vizcaino web and The site del CPC for more details.
5.- CD-AUDIO AS A CPC TAPE.
This isn't the most elegant way but some groups of 8-bits user are using. It's a fashion for using games downloading from internet very easy.
You'll save the sound of a CPC tape like CD tracks, so you'll plug a discman to the CPC tape port using the tape cable and execute like another tape. If we use the maximum speed no problem (no tape noise).
If we have an image of 3" disk, DSK file, we'll follow this steps:
Extract the file from DSK image, use CPCFS.
We introduce each file in a WAV file using CPC2TAPE in the right order, this is easier using diferent numbers.
Burn the wav like tracks using a burning software (nero, CDR-WIN, linux console, etc.). I recommend you to add a second pause between tracks.
CDT is a variant of TZX Spectrum tape
image format for CPC, this use other extension for avoid errors.
If we have a digital image of a CPC tape, CDT file we'll follow this steps:
Rename extension from CDT to TZX
Use Taper (linux versión avalaible) to convert this in a .VOC digitalized tape. Try also PLAYTZX (for linux or DOS)
Convert this file into a WAV using an audio software like Goldwave or Cool Edit.
Burn like tracks.
This is the better method (all the steps are digital) but some variants may be useful:
Plug the sound card line-in to
your CPC tape port (output line).
Save the sound of tape this like WAV files playing the tape from the CPC you
can use SAVE command or a backup software like Discology in order to get
fastest speed. This is an useful way to pass info from CPC.
Plug the sound card line-in to
your radiocassette phones port.
This is the worse method, if the tape has error the CD will also have.
Use first a CD-RW and check this is right, after you can copy into a CD-R.
For use the CD into a CPC-664 or CPC-6128:
Type:
|TAPE
RUN"
PRESS PLAY THEN ANY KEY.
Put the CD into the discman.
Select the track where the game starts.
Press PLAY in the discman.
Wait...
I think these CDs will be usable in future CPC emulators. Now you can extract the tracks in WAV files again and read this with Arnold or Multi-machine.
See also manual de ultracargas para Spectrum (on Spanish, use Google translator) incluyed into Espectrum Hoy, here you can see the way to plug the Spectrum +2A to a tape/CD player this may help us for plug a discman to Amstrad CPC-464, CPC-472 y 464+ models (all this computers have a cassette player but no tape port). We don't need type |TAPE in Models without 3" drive.
See also Emulatronia experiment also based on Spectrum.
You'll also try with MP3 files into an ISO9660 standard CD-ROM, playing this into a MP3 discman. Use a good bit-rate.
I recommend you FrontBlade + BladeEncoder, because it easy for use and configuration and we get good quality and high compressed files. The first one is a frond-end of second one.
If you are a GNU/Linux use try BladeEncoder for Linux.
There are other methods like plug a 3" drive on a PC or a 3 1/ 2" drive on a CPC, made an RS232C interface, but these ways are complicated, expensive and very dificult to make and get components, even in the market of second hand, so I prefer the last mencioned ones.

Anyway, if some is interested in these ways, refer to the technical documentation of the CPCEMU of Marco Vieth, that talks about these topics, CPC plugs document and also to the CPC FAQ (questions of more common use with their answers, on English, French & German).
IMPORTANT: We could have the files of a
program tablets in a ZIP without more, as if they are some files
more than MS-DOS, but this has a great inconvenience: only CPCEMU
is able to read these files directly, so it's more interesting have them into a DSK file,
like an image of a 3" disk, so almost any emulator would be able to read
these files.
For this there is two programs:
CPCFS v:0.85.3: powerful file manager. Introduces and extracts DOS files on DSK files. Windows 95 users would be able to be problems because it works with a command line, MS-DOS users might not be problems.
Transfer (c) Christian Horn: puts DOS files into a DSK file. Easy to use.
(c) 1999-2003, created by Jesús Basco for Amstrad CPC for beginners (http://www.cpcbegin.tk)