I currently have an IBM 600E (PII-400, 128 Megs RAM, 6GB HD) and have been experimenting with various distros on it.
With my laptop Slackware
would not install for various reasons, possibly hardware related. Puppy
works great, even running from a CD. DSL
also ran well from the CD, but personally I just prefer Puppy. Both Puppy and DSL found all the hardware etc, and my wireless connection in Puppy took less than 5 minutes to set up
Puppy is about 83 megs, complete, while DSL is 50 megs, also complete. Personally I was quite surprised by just how complete a desktop you could get in less than 100 megs.