Basically you are probably just not meeting the minimum specs in some way - probably your graphics card - OR you have some hard drive issues.
However if you are well within the recommended spec, have plenty of hard drive space and a high spec graphics card, then its almost certainly a small portion of your hard drive causeing the crash, with corrupt or bad sectors. Run disk checking utilities to scan and defrag the disk, and if theres too many problems, you may need to format it and re-install windows, otherwise you may find other programs will cause these kind of errors in the future.
HOWEVER don't panic - its unlikely, because you siad you got it to work a third time, but it was very sluggish and laggy. Because of this I'm 99% sure you're just not meeting the recommended spec. In my opinion the minumum ones are a little tto low anyway, even on a decent pc frame rates are still slower and lag more than most professional games - I tend to get 30fps whereas on DoomIII and halflife2 I can sometimes get nearly triple that...
Either way its not the fault of the trial as such, its the fact that you're trying to get your computer to do something a little too complicated for it, and that can make it run out of memory or even overheat, and if so Windows will usually freeze and your pc may even shut down to protect itself. It won't do any Major damage.
