Unixxx,
IMO the WGA kit is a better value if you are considering purchasing XP Pro rather than going back to the XP Home license that came with your Dell. Here's why:
1. The "normal" retail price for an XP Pro retail upgrade is $199. Occasionally I have seen them advertised in the USA at major electronics and office supply retailers for $149-179 with rebates. The best price I've ever seen was $99, but that was just once. The WGA kit is $149 USD delivered.
2. The WGA kit is a Full Retail license for XP Pro. This means that it is not tied to any particular computer and can be moved from one computer to the next without limit, as long as it is activated on only one computer at a time, and it does not need any sort of qualifying previous installation of Windows in order to install. This type of license offers you the most flexibility in installing and using XP. The XP Pro retail upgrade is an upgrade and will always need a qualifying previous installation of Windows or the CD for same to install. Therefore it is a less "liberal" license for XP.