Recently my pc has become rather dodgy.

After switching on and the computer is active... strange things happen.. my usb keyboard. becomes un responsive.... sometimes the broadband...

Even starting the computer has been a problem.. sticks on bios detail page..

Has any body heard of something similar? Could it be PSU or motherboard problem?

Unplug your USB devices one by one to see if they are causing issues. A bios update and firmware updates everywhere may help but use caution you don't want it freezing when you are updating. Could also be a dodgy USB cable.

Other thing to do is reseat everything such as your memory. Maybe your CPU needs a reapplication of thermal paste. Could be a heat issue....

If it's freezing before the OS starts it's def hardware.

> Even starting the computer has been a problem.. sticks on bios detail page.. 
 
This sometimes happen while booting my old pc. In my case, the video card got lose and needs a bit of pressing and a reboot is fine.

I would check out the power supply - I just went through similar issues with one of my computers, and it turned out there was just a tad too much drain on the power supply, and it would manifest in different ways - different devices wigging out or not being detected.
 
I ended up getting a new 750 watt power supply for it, and all is well again.
 
I figured it out by disconnecting lots of devices and then it started working right, and I would try different hardware combos and things would work if not too many things connected.
 
Bob Bone
 

Hi thanks for all of your replies....  really appreciate this 
 
Might be a good idea to change both motherboard and psu..
 
Only other evidence that has occurred was that my external (powered by adapter) hard drive would also drop out...  lose its usb connection and become blank..
 
My house electric line could have been hit by lightning last September and my telephone wire was defnitely hit since it messed up the router... (computer worked fine after even though it was connected via ethernet cable!) so would it affect psu or the board?   By would these problems take so much time to occur?

You don't have USB suspend enabled, do you?
http://helpdeskgeek.com/windows-xp-tips/prevent-windows-from-powering-off-usb-device/
 

As other have suggested, I'd eliminate the cables and reseat everything in the machine before I'd think about replacing motherboards and such. Good call on the thermal paste heat issue, I've had that happen to me. Also, consider running a full memory test to eliminate issues there.
 
Sometimes though, it really is a hardware problem. To check if your power supply is taxed too heavily, unplug devices and pull PCI cards to see if things stabilize. I suggest you do things one at a time to help you identify the problem more easily.

slartabartfast
You don't have USB suspend enabled, do you?
http://helpdeskgeek.com/windows-xp-tips/prevent-windows-from-powering-off-usb-device/
 

 
He gets issues before he boots windows...

hi.. so psu problems it is

Any suggestions in regards to a Psu?

I need 750watt. and possibly 6 satas. and board has a built in firewire too.
gfx is a BFG NVIDIA 8800gts 640mb..

Totally confused about rails n voltages tbh!

What makes you conclude it's a PSU problem?
What did you try here?

Cheers..