You should upgrade!!
I am an avid gamer, and I use Win2K pro.
First of all it is more geared towards business or server related use, but it also has a completely new re-written tcp/ip stack that is MUCH faster than the one used in win98 or 98se, in other words, the internet is faster. A lot of people say that many peices of software, and games will not work on win2K or that because of the HAL in NT bases OS's you will not get very good framerates in games, but let me tell you, I have a celeron 366 192Mb pc-100 RAM, a voodoo3000 pci, and I play a lot of games on my system. Basically Win2K may be based on NT but it no longer has a HAL (hardware abstaction layer) therefore, software(such as a game) can communicate directly with a peripheral (such as a graphics card, instead of having to communicate via the HAL. Also most all new games are written with Win2K in mind, and many older games, i.e. games released before Win2K, have made patches available on their websites.
These are the games that I have played on my Win2K machine:
1.Unreal
2.Unreal Tournament
3.Half-Life
4.C&C Tiberian Sun
5.C&C Red Alert 2
6.Tony Hawk Pro Skater 2
7.Rouge Spear
8.Motocross Madness
9.Monster Truck Madness
10.Quake I,II,and III Arena
11.Need for Speed III
12.Mech Warrior 3
13.Jane's Flight Sim IAF
14.Soldier of Fortune
15.Diablo II
16.and there are more that I just cant think of.
Just to wrap up, I would say that you should definately upgrade, because of the overall performance increase. You will never have to deal with your system hanging up and having to unplug it to restart, if something does go awry Win2K deosn't crash, it simply tells you that it will write a log file for you, that you can look at at a later time!!