It says that none is availible because its currently being used by your current graphics card
The Nvidia Geforce 7350LE
SOMETHING YOU SHOULD LOOK OUT FOR:
The GTX 260 is a semi-power mid-range video card in nowadays market..
You need to make sure that your power supply is powerful enough,stable enough, and has the right pci-e power conenctors. Older cards like 7350LE never needed any external power connector, so it may not be availible in your pc. Regardless, PCI express x16 2.0 cards with enough power work perfectly fine in 1.0 slots, but you might not get the FULL performance boost..
May i even recommend the ATI 4870 for a very similiar, if not greater performance than the GTX 260 at a much lower price
http://www.tigerdirect.com/applicati...007&CatId=3669
I really don't understand why more people are buying Nvidia nowadays when Ati is offerring better value, its all up to personal opinion though...iguess