I have used everything from 95 to XP. In order, and solely based on my own experience;
1) Windows 2000 Pro, with service pack 4. Fastest and most reliable. What I use now. Most XP drivers also work with it.
2) XP Pro. Slower than 2000 on every machine tested (over a dozen, from 300s to 2.4s) but not enough on higher end machines to worry about. Pretty solid as a rule, and like 2000, allows you to close down a non working application or game without crashing the rest of windows.
3) 98. Second Edition is the best.
4) ME. AoE and RoR can both crash ME when they exit, usually crashing the dibeng.dll and knocking out explorer so you have to reboot. Simple solution, ALT + TAB to the desktop and close them from there. Better for later games like EE, which trashed my 98SE install when it crashed, but ME survived and also has the restore function, later used in XP.
5) XP Home. Some have had no problems with this, for me though it is a buggy piece of junk that sees your hardware when it feels like it. Avoid.
6) 95. Would have been up there with 98 but the updated driver database in 98 makes it more stable and supportive of things like Direct X etc, plus it is no longer supported. If you still have it at least upgrade to 98SE. That won't be supported for much longer either, but for now doesn't need any support to run most things.
[This message has been edited by Phill Phree (edited 07-27-2003 @ 03:01 PM).]