Xubuntu 7.10 uses the same Linux kernel and other system files as Ubuntu and Linux Mint, which my old 600 Mhz Pentium III can easily handle.
The problem most people encounter when using Linux on older equipment is related to the Desktop. Most distros use either Gnome or KDE. Both are resource hogs. I really think that a lot of people disappointed with Linux install the latest and greatest version on an old machine only to complain about how slow things seem.
Xfce's Desktop Environment is much lighter. It handles all the normal Windows placement issues, provides panel launchers, a desktop manager, file management, (thunar is fast file manager), session management and various utilities, just like the big boys, but it is much lighter. You do give up some of bells and whistles associated with Gnome and KDE. For what I am doing that is no big loss.
Except for Firefox (which I think is a bit of a hog) Xubuntu has also selected and installs lighter applications. For example it doesn't install the entire Open Office suite, opting to install only the word processor.
For a full flavor of what Linux can do install the latest Linux Mint on a late model PC. If you want to get another few years out of an old Windows 2000 machine try Xubuntu or one of the other distros using Xfce.
I don't know for sure what the upgrade was about, but I was recently notified by the update manager that I had new updates. Several related to Firefox. I installed the updates like a good little user and suddenly my problems with Firefox in Ubuntu were cured. It could be that my problems were installation specific all along. I wish I knew.
"All you need is love."