PC wont boot and no usb power for keyboard

Hi. My PC wont get past the boot stage that says press F5 etc for set up, it doesnt get to the XP bit with the black background it just hangs are the WinFast bit (winfast is my motherboard). Also the USB ports don't work either so i cant press F5 or anything. ~This is weird, ive tried replugging the power leads, everything seems OK.
I don't know what to do.
Also, just before this it seemed to have power fluctuation problems, it would not boot at all, it was like intermititant power, allmost like it was being switched off and on every 3 seconds, i took out the power unit, cleaned it and put it back in and now i have this problem.

Can anyone help me> If you need anymore info ill be happy to provide it.

thanks

 

Try taking battery out of motherboard for a few minutes and try again, possible bad mb or psu. Taking battery out will restore bios to default. ed

 

thanks, its weird, after about 5 mins of leaving it running it eventually boots windows!, i first hear the floppy drive whurl up and then it goes black for a while and then it is the XP screen as normal. then a further pause for a minute and i eventually get my log in screen, it seems to run fine. i took batt out and made no difference. i rebooted a few times and its the same.. i wait 4-5 mins at bios startup bit and it goes through same process.

there is a slight electrical burning smelll coming from the power unit i think, this cant be good =/ but its still working lol

 

Im not sure id be laughing about a burning smell, as that is something frying in your CPU. I was originally going to suggest your Hard drive as if it posts to bios then your mobo is working fine.

But as far the burning smell, im not sure what to do :|

 

if i was you I turn the computer off to be safe sounds like the power unit is on its way out. if you leave it running it might effect the mobo and the cpu and then you will have the whole computer to replace but turning power off you only have the power unit to replace and saved the rest of the computer.

 

Yup, sure sounds/smells like PSU is about to die or could even be a capacitor on your motherboard blowing.