Well you didn't say anything about a video card, but assuming it meets minimum requirements for X (
www.xfree86.org ) having a gui shouldn't be a problem.
Any distro will do, A pentium 133 is relatively fast for what linux runs on happily. I'd look at maybe Gentoo (not REAL easy to use for a n00b) or Redhat, an older version though, maybe 7.3 or so. You could also try Knoppix to see how it goes, if all goes well, Debian might be a choice to consider, or just thrown Gentoo onto an HD and use it as a regular distro not a CD based one.
HTH
Cool
