It doesn't look like you have enough RAM memory for Xbuntu:

"To run the Desktop CD (LiveCD + Install CD), you need 128 MB RAM to
run or 192 MB RAM to install. The Alternate Install CD only requires
you to have 64 MB RAM. To install Xubuntu, you need 1.5 GB of free
space on your hard disk. Once installed, Xubuntu can run with 192 MB
RAM, but it is strongly recommended to have at least 256 MB RAM.

It seems most Linux distros need or like at least 256mb Ram, but you
can try Puppy Linux which works better from the CD rather than a HDD
install. I use Ubuntu for my modern machines, but for Pentium 3's I
use PCLinuxOS which runs better on those.

Puppy Linux: http://www.puppylinux.org/

And of course there's always DSL, but I can't see how anyone but a
techie would use it, or need it. The graphics remind me of old DOS
screens.

http://www.damnsmalllinux.org/