I agree. You'll get the most bang for your buck (figuratively speaking) out of those old machines if you run a Linux server. But to really do it up right, you might need to abandon the GUI and run from the command line.
If you're just looking to run a low-traffic HTTP server and not much else, you could probably get away with NT4. Even Windows 2000 will run on a Pentium II, though not especially well. Keep in mind that the more services you stack (FTP, e-mail, etc.) the more performance will degrade.
If it was me, I'd give Ubuntu Linux (or its parent distro,
Debian) and
LAMP a shot. It'd be a fun project, if nothing else. And free.
Here are a few "Linux on an old PC" links I found whilst Googling:
http://en.wikipedia.org/wiki/LAMP_%28software_bundle%29
http://www.smallbusinesscomputing.co...le.php/3346331
http://www.webpronews.com/expertarti...r-of-an-old-pc
http://www.howtoforge.com/ubuntu-home-fileserver
http://www.instructables.com/id/Make...-Of-An-Old-PC/
Whatever you choose, good luck, and let us know how it goes.
