I found two links suggesting you can make your Belkin card work using ndiswrapper. Here are the links.
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http://www.ubuntugeek.com/howto-inst...on-fiesty.html
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http://www.linuxquestions.org/questi...478/page2.html
There are different ways to get wireless cards to work. The best is a native linux driver. If one can not be found, then ndiswrapper allows you to use a windows driver, ndiswrapper provides an interface between the incompatible windows code, and linux. It works on lots of cards.
I run Slackware on a similar vintage desktop, its a P4 at 2.0 Ghz. It works well enough for an XP vintage system. You have enough ram, the disk space might be a little tight for a larger distro. Most will install, but you won't have much space left over for user files.
If you plan on keeping XP, you will have to shrink the XP's partition, and create a new one for linux.
Things you might consider, buy a new drive, and swap out the old one. You will find it difficult to find a 40 gig drive these days. There should be lots of larger drives that will do the trick. Then you could have the entire drive for linux.
If you have to have XP, then re-partitioning is the best solution on the old drive.
You could also install v-box, and install linux as a virtual machine. This does not require re-partitioning. You install v-box for XP, and linux becomes the guest system. You will need a 10 gig partition for a useable system.
As for the "Which distro" question, this link might help.
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http://www.tuxradar.com/content/how-...t-linux-distro
Hope this helps.