Can i run an ATI Radeon hd 5850 in my pc?

aye you can run it (depending on how new the PSU is, count 10% less W every year its old) but its better to get a gtx 460, its cheaper and just slightly slower then a 5850, but its smaller, uses less power and more quiet then the 5850 ^^ so its a win win win with gtx 460 (as long as you dont really 5850 it will work fine too ofc)