need computer expert advice!!!

i need some computing advice here, really hope that i can get some feedbaack soon, lately i tried a online game called mo siang online, really fun, but what makes me mad is that whenever i play that game on my pc, the screen will suddenly go black and i have to restart the computer, i tried tweaking the security systems and firewall, and also re-installing but none of that seems the solve the problem, the funny thing is that it runs smoothly on my 4 year old comp but not my new comp(with the nvidia 8800GT), i've tried looking in forums but no solutions have been posted, so if anyone knows what to do or you just know a computer expert, just let me know,i thank you in advance.