If you have a free PCIe 16x slot open, shouldn't be any problems fitting it in. Your only concern should be, the PSU, does it supply enough wattage for a GTX280.
We bought a 600 Watt power supply and installed after the first one went. Now we are trying to install the video card. Its is quite large but we got the room. This is going to be our CAD computer for a small company I work at.