My 4.5 did the same thing just before chrimbo. I still think it was a Virus hiding itself as the computer refused to write discs and everytime you opened a program, it illegal errored out straight away, so eventually I had to reformat and start again
So now, I keep a backup Windows installation on a separate H.D. and just transfer the files across if I have anymore problems...
P.S.: Cactus, you tried to send me a P.M. a few weeks back, but my inbox was full. You can try again now, i've emptied it. Cheers bud, LUFCfan