The first thing to do before upgrading is to make a full system backup of
your current setup if you can. If not then at least backup your important
data. Upgrades sometimes do not turn out as expected. While you can
obviously upgrade from Windows 98 to XP using the XP Upgrade version (see
here
http://www.aumha.org/a/xpupgrad.htm ) you would be better off if you
have an actual Windows 98 CD. The reason I say this is if the upgrade
doesn't come off as well as you'd like you can still use the XP Upgrade CD
to perform a clean install. But you need to have a Windows 98 CD to offer up
when prompted for a qualifying product.
You say you are the registered owner and have registered the copy of Windows
98 that is on your system. If this is true you can borrow another person's
Windows 98 CD (providing it is the same version as yours) to satisfy the
request that your new XP Upgrade version will ask for during a clean
install. When you bought Windows 98 you actually bought a license to install
it and that is what your Product Code entitles you to. The disk itself is
just a piece of plastic with the code stamped into it but the Product Key is
what matters. So as long as you have the Product Code written down for your
registered Windows 98 install you can use any Windows 98 (same edition) CD
with that Product Key. When doing a clean install with the XP Upgrade you
won't be asked for a Windows 98 Product Key only to insert the CD itself for
a few moments but having the Product Key means you are licensed to use
Windows 98 as the qualifying product. If you need to uncover your current
Windows 98 product key you can take this link and scroll down to "Product
Key"