can GTX 260 run with 250 watt psu????

no, look at it this way. i had a gtx 260, running under a 550w (not cheap psu). then i replaced it with a 560Ti which consumes less power than the 260. and a 550w was i believe borderline for a 260.

don't risk it, and having a 250w psu means that it most likely be an old psu, so factor in capacitor aging and you have less than 250w capacity