Windows 2000 is a decent enough OS and would be awesome if it ran older games well enough. Here are a few I ran into trouble with:
NFS High Stakes - requires much pain to install and usually won't work.
NFS Porsche Unleashed - has memory problems.
Rune - sometimes the graphics get messed up, everything looks white.
Quake 2 - save games won't load.
Its usually the older games that give it a fit, new stuff will work fine since they were designed for 2000 support. Networking is good for 2 or more machines together but for general net use there isn't much difference. Getting a 98 computer to share files with a 2000 machine is hell.