...reseating the motherboard, or reseating all the power connectors such as those on the hard drive, or CD drive, etc..
If you are capable of doing these things, open the case, and do them.. If you are not, then I suggest taking it to a reputable computer tech near you.
Hope this helps.
I just moved (relevant because last time I moved my computer also had problems) and my desktop is having the following issues: on and off recognizing keyboard is present; recognizing external cd drive, but drive is having errors and can't access anything in the drive from the computer; wireless network adapter is recognized but the software is not working properly and no networks are being found (the network is working fine. I bought and returned a different adapter for which the software worked on the first installation but did not work after restart). After the last move, the problem ended up being the hd had somehow come loose, no one is sure how that occurred. I think something may be loose again, but it's obviously not the hd and I don't know enough to know what to look for.
My computer is a pc homebuilt from parts (I was not the builder) running Windows XP. I hope you can help me, I haven't been able to use it for a couple weeks now.