Games freezing/crashing

I doubt its the GPU because i just researched your GPU and compared it to Fallout 3's minimum requirements and its way better... Is there a soundloop though when the game freezes?

go into bios and make sure hpet is enabled (high precision event timer) it may also need setting to 32 or 64 depending on the bit rate of your o.s (64 for 64bit)
save and quit.
turn off anything like easytune or other software based overclocking software and update your gfx to 12.10 drivers.
make sure you have the nfo chipset identifyer supplied by your motherboard manufacture.

lastly check the event logs. in ctrl pannel/admin tools/events/applications.
look for erroes arounf the time the game crashed not form 2-3 weeks ago.
list them here... if there are a few list the last 2-3 of them.
if your see error 41 it means you turned off the pc without shutting down properly so you can isgnore that unless you didnt switch off by the power button.
if you see error 124 then its likely your memory or cpu isnt getting enough power due to a bad overclock.