Hi!
Just sold my 560 ti 448 windforce and started using HD 2500 (i5 3550). After about 10 hours of constantly freezing i finally solved the problem. F9 bios is set to 1150 mhz for HD 2500 and that is just wrong. HD 2500 is using 650 mhz clock! I lowered igpu clock to 650 mhz and all my problems went away!
HD 2500:
http://www.intel.com/support/processors/corei5/sb/CS-032273.htm