you need to upgrade your PSU
do you live in the USA? Do you have a budget for the upgrade?
That is not enough power supply for a GTX460. Even high end power supplies are cutting it close with 400 watts. Look for Corsair, Seasonic, Antec, PC Power and Cooling or XFX and you would be better off with 450 watts or more. Realistically a good quality 550w unit can run any single graphics card made so if you plan on updating in the future you might want to consider that.