Which Ubuntu version is suitable for an Intel Pentium 3 Processor?

Solution 1:

Your best option (and most likely your only option) would be to go with Lubuntu 12.04 or 12.10. I have it installed on one of my old Pentium 3's with about 160mb of ram and it works fine. Not the quickest but definitely usable on a day to day basis.

Just remember that its not only about the operating system. The programs you use also has a huge impact on the usability. Lubuntu comes with fast and light weight programs which makes the system very usable on a day to day basis. You should even be able to do some multitasking with easy for example listen to music and browsing the Internet.

Solution 2:

Definitely Lubuntu. I'd recommend that you use the alternate install from this page. The alternate installer does not use the graphical interface, so requires less RAM and will run faster.