Windows 98?? You mean there are still people using that shit?
The only OS I can think of that is WORSE than Win98 was Windows ME. While it is true that Windows 2000/XP use more system resources and the like, it is worth it.
I have to agree with Dagok that Windows 2000/xp is FAR MORE STABLE than any previous MS OS.
I can leave my WinXP system running for months without rebooting. I can install all kinds of games and applications, change hardware, change drivers, and do almost anything I want and WinXP keeps running fine about 99% of the time.
I still remember how Win98 would blue screen and crash just about every time you changed anything. It sucked.
And if your computer is too slow to handle Windows XP then you sure as hell aren't going be able to play Doom 3 very well. Windows 2000 was nice, and XP is better.
Drag your anachronistic ass out of the 20th century and get Windows XP.