"Windows has been shut down to prevent further damage"
First time I ever saw that error message was when I mixed two types of RAM, and most times I find that it relates to RAM or data corruption.
Simply re-seating the RAM often makes the difference.
Good post just yesterday, where a poorly performing computer was immediately improved by re-seating the old module adding more RAM and changing the flat 40 wire IDE cables for 80 wire, cross-talk-screened, cables.
So what other things can be done to improve basic performance? (Not so much the processing speed but the general capability of the machine, without changing the mainboard and processor.)
A faster drive with a bigger drive buffer is one. The higher speed increases paging file performance and the bigger drive buffer can increase the speed of defrag four-fold (very noticeable with Windows ME) simply by changing from a drive with a 2 MB buffer to one with an 8 MB buffer.
I would love to see the change in defrag speed between a drive with a 2 MB buffer and one with a 16 MB buffer!
TweakUI can speed up menu opening times and response to the mouse pointer and setting the right screen refresh rate makes a perceptible difference too.
Anything which says System Works and has a lot of gadgetry starting up when Windows starts certainly does slow things down in my experience, and are better avoided.
I've re-installed System Works or Utility programs on many occasions so that NOT everything started up with Windows, just those parts of the program which are essential.