Originally posted by me on the mass effect 2 forums (scroll down for the - possible - solution) ---STORY So i have the same problem as everyone: dual core CPU, but only one core was being detected, causing the game to malfunction. I came from windows xp sp3 ultimate, and i decided to get windows 7 as a solution (seeing my friend had win7 and his game runs flawlessly). However, i installed the 32-bit version (don't know 100% sure if that matters) and still only one core was detected. But it seems like there's no Detect HAL option in win7 either! I googled a bit and it seems like many people using win7/vista are experiencing this problem. I thought that maybe installing the 64-bit version might work. But dear lord, fate strikes again: after the 64-bit install goes all the way to 100%, my PC reboots but gives an error trying to boot win7: "Unexpected error blah blah blah some-error-page ... ERROR: 0xc0000225" So i googled for that error and again, many people using win7/vista are expeeriencing this problem, mostly after a fresh 64-bit install. Then i encountered a topic about some guy saying that the technicians from the shop told him that his memory timing was bad, and he had to set it manually to 1333MHz So what i did to get win7 64-bit to work: ---SOLUTION Get into BIOS and look for your Memory Frequency, set the mode to MANUAL and then select the highest frequency (probably 800 or 1033 or 1333). [I ALSO DID THIS: go to power interface in BIOS and ENABLE APIC, however i think the real problem was caused by the memory frequency] [Note: enabling APIC may cause linux operating systems to fail. Just disable it again to use them] Make sure you SAVE before exiting BIOS. Can anyone confirm this works? NOTE: haven't tested wether ME2 actually runs perfectly, but i am 100% sure that my 2 cores were now detected.