You don’t say what operating system you have, but I have mostly found drivers for XP for this card. There also appear to be different versions, Rev.B and Rev.C, and a DWL-G650+ so you need to look at the card and check you are getting the correct one to match.
Try entering ‘dwl-g650 driver download’ on Google. It gets many hits, and the top few will have the different variations of the driver for you. If you have a different operating system from XP, then add the OS name to the end, such as ‘dwl-g650 driver vista’.