1. The software way (use Internet Connection Sharing=ICS) on the Vista laptop. Details, for example, in http://windowshelp.microsoft.com/Windows/en-US/Help/bfd3bd31-82f0-4b9c-9cde-fb92bc2b14771033.mspx
2. The hardware way: Add a wireless card to your desktop, so it can run independently of the laptop. Here's one: www.newegg.com/Product/Product.aspx?Item=N82E16833315041
Note this is not a recommendation for the seller nor for this particular product. You can find many comparable products (also connecting to USB, if you prefer) and all shops have them.
If you already have the wireless router, I'd recommend to go the hardware way. ICS, although working, is somewhat outdated (it used to be useful in the good old days of dial-up).
Hope this helps.
I'm pretty knowledgeable when it comes to computers but despite my greatest efforts I simply cannot get this to work... here is the situation
I have a desktop sans Wi-Fi capability running XP pro SP3 that I've got hooked up via ethernet to my laptop running Vista Home Premium SP1...
My question is how can I use the wi-fi connection on my laptop to give my desktop internet?
I already have my Wi-fi connection set up to be shared... I've tried manually setting the IP addressed to something like 192.168.0.1 and 192.168.0.2 and then setting the gateways to each other... that didn't work... and I've finally given up, any help would be appreciated.