Acer aspire 2930 windows 7 auto restart?

i recently encountered a problem with regards to my acer 2930 laptop.i have windows 7 beta o.s installed already when bought.i bought it just December 2009..recently,i'm encountering problems with regards to automatically restarting every after approx. 2+ hours or something. it shows illegal operation...cant read the whole thing though.i tried disabling the automatically restart after system failure but it wont work,it even did shut down instead.i browsed a few forums but none of it worked for me.i even had bought a cooling pad for my laptop.can you please help me..thanks in advance.