You shouldn't have compatibility issues, but you may run into power issues. If you purchase the card and the PC keeps restarting during Windows boot up process then you have exceeded your Power Supply's max. I don't suspect that will happen but it is possible.
If that does happen, I would look into a 500/550W Power Supply. Try the card first though.
Humans are the only creatures that won't live up to the their potential. Give everything your all. When you die, die on E.
So I ask you, what do you intend to do now?