I am installed Debian Linux, on my old celeron 366.
I put 256 ram in it with 2.5g HD,
for a 366mHz system it runns pretty quick, I think I may duel boot my .
Debian comes pre-installed with Gimp, OpenOffice.ORG(which I have been using at work, I recamend it), and a ton of other programs. All LEGALLY FREE!
and the big bonus for you paranoid people. Virus' usually do not attack linux based systems. People think attacking microsoft is much more worth while.