Here's an odd one. Pc freezes-

[frenchscottie]

Here's an odd one for you guys out there.
I have 2 pc's with a KVM switch. One a dell and one I built a few years ago. Both are P4 3.0
My non dell started to freeze to the point of having to reset. It would then work for a while - minutes or hours on the odd occasion. So I thought could be the graghix card so I borrowed one and installed it - but no still the same. Then one day I was doing a search for a file and it froze but the search was still working, ah I thought the kvm switch so I unpluged the mouse and plugged it in to a usb port - but no still nothing. And the same with the keyboard. Next I did a memory test that was ok. So I thought maybe the mobo as I had the sata ports fail on me intermitently so I had to put in an ide hard disk. Or maybe it's the hard disk as usually when it freezes it's accessing it. (except for the time I was searching). So I had an old 40 gb ide so I put it in and installed vista. Other pcs have xp. So I booted up into vista. Now what happens is the mouse and keyboard stop working - but if I unplug them from the kvm switch and plug them into usb ports directly I can use the pc. Thinking it might of been a cable fault I swapped the kvm cables round from dell to other and vica versa. But it still does it.
Whew there you are. Any one any ideas?