If you want to play DOS games in 2k/XP, I suggest trying DOSbox. It's a DOS emulator that runs a ton of software and supports all kinds of old hardware. It even runs protected mode games (in the CVS build) like Duke3D and Doom. It's at http://dosbox.sourceforge.net/
Also, upgrading your OS in respect to Windows is sort of like buying a new television. Sure, your old one works and does its job, but a newer is much nicer with more features.