What linux version for old pentium 3 laptops

I have around 25 old laptops and am looking for a suitable version of linux to install the CPUs are Pentium 3 or Celeron from 500-1000MHz and RAM is between 128-512Mb. Some have DVD drives so I am looking for a version of Linux that will run well on these machines, recognise the hardware without complicated driver installation, have software that can play DVDs and have or support a browser that supports flash. Please let me know what you recommend.

have you tried Ubuntu 10.04? you could test it by using the LiveCD option on the installation CD.

The distribution doesn't matter so much as your configuration. You want to use a pretty basic desktop environment to make the most use of those machines' limited amounts of RAM. I'd pick LXDE or XFCE as they use a lot less RAM than Gnome or KDE. Most distributions come with Flash or you can add it after the fact pretty easily; the same is true for a DVD decoder. Hardware detection is generally pretty good but laptops and old laptops in particular tend to have some very odd hardware that wasn't even well-supported in Windows let alone Linux, so you might have problems like all of the buttons on a non-standard keyboard not working properly or suspend/hibernate not working properly.

If I had to recommend a specific distribution, Debian would be good. It's stable, doesn't use a lot of RAM by default, is fairly easy to install, and can be configured just about any way you would want to. You'd want to scroll down to the alternate desktop environments menu item at the CD boot menu to select something other than Gnome, use the graphical install option, and make sure to check the "use non-free software" box when asked that question during the install.

Ubuntu likely ran like a dog since it assumes you are running at least a somewhat modern computer and can use more RAM than some of those machines have. It would run okay on a machine with 512 MB of RAM and a 1 GHz PIII, but would run poorly on machines with less than 256 MB of RAM or ones with CPUs nearer the 500 MHz mark.