Step 1 – Verify all your XP systems support WPA
You can tell if your XP system has the updates by right clicking on "My Computer" (located on the Desktop or Start Menu) and choosing "Properties." You'll see a screen pop up that looks like this:
Note the "Service Pack #" listed under "System."
-If the number is 2 or 3, then your system is up to date with WPA compatibility.
-If its 1 or not there at all, I strongly recommend going to http://windowsupdate.microsoft.com and installing the latest service pack. Otherwise, you're leaving yourself wide open to all sorts of vulnerabilities that MS fixed in those Service Packs and you probably shouldn't be connected to the internet.