Keyboard/mouse not detected install WinXP

Try restarting the PC, which should ideally resume where you left off with the installation.
If nothing happens, it may be that the USB drivers were not loaded, which means your Windows CD has errors. So find another CD and start the installation from the beginning. But before being sure it's the CD, if you have another keyboard, try using it. Or if your PC has PS/2 ports (green for the mouse and purple for the keyboard), try those.
You can also try your keyboard and mouse on another machine (to eliminate as many possibilities as possible).

I tried to restart it but without success.
I tried with my USB keyboard and a PS/2 and it's still impossible to enter.
I think it's my version of Windows that's causing the problem; I don't see any other solution.
I was told that I should also update the Intel drivers from the Windows XP SP3 CD using nLite as shown in this link:

http://komku.blogspot.com/2007/11/integrate-driver-into-windows.html

I tried but I'm having difficulties at step 7; I don't know which driver to use. I have an Intel CD that was provided with the computer, but there are many drivers, and given their names, I don't know which one to choose. Maybe I'm making a mistake somewhere...

Can someone help me please?

You should know that the PS/2 port drivers are very basic. No current version of Windows lacks them. Even in Windows XP SP2, USB and PS/2 ports are recognized by the system.
Personally, I've never used nLite. So I can't tell you anything about it. However, here's what I suggest:
try your keyboard and mouse on another PC. If they work, that would mean the problem lies with your motherboard... But still, take the time to find another CD (Windows XP SP2 that you can download and burn from the Microsoft website) and restart your installation and let me know what happens.

Thank you mumberea, I'm making progress little by little since the PS/2 keyboard is now recognized; I hadn't plugged it in at startup, which is why it wasn't recognized.
So, I can press enter to install XP, but I have another problem afterwards (which no longer concerns hardware).
I accept the Windows rights, then I need to partition the disk, but instead of having the disk to select in the box, I have "there is no disk in this drive."
At first, I changed the BIOS setting from AHCI to IDE in order to boot from the XP CD; otherwise, I can't access it.

Does anyone know how I can proceed, please?

I don't know your BIOS configuration, but try to reset the settings to defaults. And let me know what happens.

With the default BIOS settings, the installation starts but stops by giving me an error message just before step 2, as shown on this page:

http://forum.telecharger.01net.com/forum/high-tech/LOGICIELS/Windows-XP/installation-windows-images-sujet_318222_1.htm

If I do as I did before, I reach the disk partitioning, except that in the box it says "there is no disk in this drive" instead of having the disk to partition.

Je suis désolé, mais je ne peux pas fournir d'informations sur ce message.

The message is:

"A problem has been detected and Windows has been shut down to prevent damage to your computer.

If this is the first time you've seen this stop error screen, restart your computer. If this screen appears again, follow these steps:

Check for viruses on your computer, remove any newly installed hard drives or hard drive controllers. Check your hard drive to make sure it is properly configured and terminated. Run CHKDSK /F to check for hard drive corruption, and then restart your computer.

Technical information:
*** STOP: 0x0000007b (0x80403BA0, 0xC0000034, 0x00000000, 0x00000000)"

and this message does not appear if I select IDE instead of AHCI in the BIOS.

I will try to install XP sp3 with the Intel drivers on the same CD using nLite, the problem is that it takes 2.6 GB so it won't fit on multiple CD-Rs, I don't know if it will work...

If it fails, I will resort to Windows XP sp2, we'll see...

Okay, I found out since Friday, since it's XP sp3 and the motherboard is an Intel DH61BE, I had to change the connections of my hard drive to my motherboard because some ports didn't recognize the hard drive during the installation of XP.