XFX 9800GT 512 (HELP!!!!)

Hi there I've recently had to buy a vid card as my old1 went bye bye
I was running PNY 9800GT 512 PCI E x16. Now I'm running win 7 64bit and it blue screened and restarted and windows had shut down vid card but still used vid card monitor port as mb does not have 1 and the fan still running on it.
Anyway I bought a second had XFX 9800 fitted the new card after removing all old drivers and flashed bios but when I switched it on the monitor did not come
Dunno why. But when I put old card in the monitor was fine and came :-(
Have I bought a duff card or am I doing something wrong
Please help me