What are your display settings set to? Are they all maxed out? Just to give you an example, I run a P4 1.6a overclocked to 2.4 GHZ, Geforce 4 Ti 4600 and 512 MB DDR Ram running at 400 MHZ. With the settings maxed out I only get about 30-35 FPS at 1280 x 1024.

Also, I run FS2k2 on my laptop which is by no means a screamer. P3 650 MHZ, 320 MB ram and a 16 MB video card. This is also running XP Pro. This bounces between 20-30 FPS at lower settings. It does not stutter at all.

You said "it stutters now", what did you change? Did it run fine on a previous operating system?

Make sure you do not have all the eye candy turned up. Like I said, it is VERY cpu intensive and your 1 GHZ might not be able to handle it with the graphics you want, even with a top of the line video card. Try a simple defrag as well, sometimes works wonders.

If this doesnt work, try stopping some processes as you said. First starting with any anti-virus program. They are known to be resource hogs.