justmoazzam :
can i install XFX 9600 GT on my dell optiplex gx280 having 305 watts psu?
i dont think you'll have any space at all and most slim desktop provide mini atx power, so first check if there's any pcie slot first(which such model rarely seem in the series since it is mini atx) if it does then buy yourself a new case (mid tower or standard, not mini tower!!!) and a decent power supply( at least 450watt or above and over 300watt at 12v+ rail combine power when maximum load.) and it will also require 6pin pcie plug too. 305 watts mini atx? you can't be serious....
PS: since gx280 is a really old system, and most of model did offere only ONE pci slot for expansion purpose. and some model did offere editional agp slot, so even if luck you'll probably end up have to get a agp card, and most likely it would be agp 4x. which means you need a new system.
jay2tall :
It might be pushing it a little. Have you considered a 4670, it uses less power than a 9600GT and would be a "safer" bet with similar performance. A 9600GT is a nice card, but I'd be concerned about the power.
problem is his mobo has no pcie slot at all(at best, agp.....but i'm not sure most of model had since many of them end up only have one pci expansion slot left.....) without pcie there is noway he can install a 9600gt on his gx280. tiny case/no power/no pcie slot/no agp slot i really dont think there anyway beside change that piece of crap.
caution: nvidia did not provide any model for apg bus after geforce 7 so he'd probably have to look up for gfx 7600s or radeon 3650.