Can someone let me in on how to remove Windows Longhorn from my
computer? It won't let me reformat the disk using a Windows XP cd,
and I can't figure out how to just uninstall it.

When I put in my XP setup cd it opens up via the autoplay to the
'Welcome to Microsoft Windows XP' screen but has the option of
"Install Windows XP" darkened out and I can't select it.

Longhorn is annoying me and I just want to revert to the XP that I
have installed underneath it.

Any help would be appreciated.