first off your english is fine, congratulations :P.

the problems you appear to be experiencing, would appear
to be heat/overheating related, either on the cpu or videocard...
could even be a dodgy ram problem, but i would say that heat
is the most likely culprit...

unless; its only happened with new/old drivers on your videocard
just recently, in wich case it could be that...

just my thoughts hope they help...

__________________
don't worry the whole world isn't against you....
just everyone in it