you used a hd5770(max ~140w) + Q6600 (max 105w) and your psu is still alive.
better option is to stay away from overclocking now and manage a psu of atleast 500w to overclock hd5770 to 1010/1390 (max stable for my hd6770) and some from Q6600.
use prime95 to stress cpu and occ/msikombuster to stress gpu at same time and then check your minimum voltage reading on 12v, 3.3v and 5v using hwinfo32. if it is getting close to 12v or below 12v on 12v rail (reading), less than or equal to 3.3v on 3.3v or/and less than or equal to 5.0v on 5.0v rail then your psu is near to blow. you may encounter a restart due to overload.