Just thought I would voice a couple of things, which I have just gone, then went .... So the GPU was overheating, and I went to get some compressed air, leaving it on sleep. Came back, opened it up, removed the GPU, and cleaned it all out... Then upon reinstalling it, dropped the screw which fell into the PSU eeek, so quickly turned off the PSU switch at the back, removed that and got the screw out, Put it all back together and booted, however was not greated with the usual login screen, but the locked screen? So I thought OMG have I broken it?? (odviousally not since it was powered on and working), started up the event viewer... and the machine had been asleep when I removed the GPU, and right up till when I pulled the plug, extremely pleased its still working, but lesson is:
1. Make sure computer is off before doing stuff to the hardware!
2. Use a magnetic screwdriver
Note, there was no real point to this, just thought you may find it funny