Geforce 9800 gtx work with dell dimension 9100
Will geforec 9800 gtx work with dell dimension 9100
It is a PCIe 2.0 card in a PCIe 1.0 slot which is not a problem.
The 450 system power supply requirement mentioned on the nvidea site is worrying though, the Dell has 375W. These things are always a bit wide and in most cases you can get away with less.
You'd have to perform a wattage use analysis on the dell to see if it has the 140 W spare.