ve a couple of options to get wireless for that desktop.

1. You can get a usb wireless adaptor that plugs into a usb port.

http://www.newegg.com/Product/Product.aspx?Item=N82E16833704053

http://www.newegg.com/Product/Product.aspx?Item=N82E16833320040

2.You can get a pci/pci-e slot adaptor.

http://www.newegg.com/Product/Product.aspx?Item=N82E16833127460

http://www.newegg.com/Product/Product.aspx?Item=N82E16833320071

These are the two types of adapters that you can get for the desktop and they come in all price ranges. I just listed these to show the two different styles and you can go into Newegg and choose the one you want. I would say that the pci slot adapters would be the better of the two styles but both will work.