Mouse and keyboard not working..

[IwantanewPC]

I needed to test the PSU from my upstairs computer in the downstairs family computer, which is a very old PC.

After I had done so I took the PSU from the upstairs PC out, put the original back in, connected everything back up as it was before but now the mouse or keyboard aren't working. Both the keyboard and mouse lights are on but they just won't work.. and because I need to login from the XP menu screen, I can't get to the desktop. I can't get in to the bios either because pressing Del does nothing..

Anyone know what might be the problem?

 

[IwantanewPC]

Neither are connected via USB... well, the mouse is a USB mouse but I've got it through a PS/2 adapter.

I tried just plugging the mouse in through USB but that made no difference.

 

[IwantanewPC]

Yeah, quite sure. Green to green, purple to purple. I'll try the CMOS.

Any more suggestions people? This is really frustrating, I just don't understand it at all.

 

[IwantanewPC]

No one?