To be honest i don understand how a pc like that cames with a 350w PSU.
First i would change the PSU, nothing less than 500w and see what you get.I searched and i couldnt find any that came with 8 gb of Ram so i suposed you might have bought more ram?If you did, its better you see what is the cicl.you might have also a memory conflict.
I would go for sure for another PSU, and then if no improvement yes try that or other GPU, either way even the GTX 260 will demand a better PSU.Nothing less than 500w it will be there for future
350w i guess those were stoped being made like 3 or 4 years ago.
Keep us posted.
