Whilst on PC Advisor with my other newish computer, when I clicked on the 'back' button a colourful screen of rainbow-type diagonal lines appeared and the computer screen just froze. I held the on/off button for a few seconds to close it down, as nothing else worked, and when I switched it on the power is there but just a blank screen. Nothing else happens, no keyboard, no mouse, no beep (swearing at it didn't work, either). I tried putting in my XP cd to repair or re-install but nothing happens. Suggestions at this point would be greatly appreciated.
do you have a pci graphic card or built in? I had a graphic card die on me with the results you list. Try opening the case and removing all cables one at a time and putting them back in just in case one has worked loose. It could be a power supply problem with one set of wires dead - this would give the impression that all was working but it isnt.
my first port of call would be a new power supply these are relatively cheap or you might be able to borrow one from someone. If you see the logo can you enter the bios? if you can it might be a fault with your windows installation.
I have just reformatted my hard disk and re-installed XP Home. Everything went to plan except, when I started the comp, and after the initial intro bumph, the desktop came up and I then put the motherboard disk in for the drivers to load - firstly the graphics drivers - and immediately the colourful screen of rainbow-type diagonal lines re-appeared and my computer froze again. Back to square one.