Well I haven't had one. A disaster that is. Just for a change .
My PC cock ups are famous and have featured here before. I tend to tinker and experiment too much.
Anyway, the PC seemed to be a bit slow lately and noisy with the fans whirring away. There were a few little bugs that my antispyware and antivirus hadn't cleared, so I did my periodic reinstall of Windows 7 and took the lid off the PC case and used an air duster and brush to clean it out. There didn't look as though there was a huge amount of dust and fluff, but what a difference! It's running virtually silently now and fires up very quickly. Nice.
I've got a bit more software to add, but all seems fine so far. I'm bound to bugger it up sooner or later though. Still, live and learn.