Have you seen
http://www.xp-refresh.net yet? They explain it all. Problem is, the website for the NVrefresh tool (
http://www.nvrt.net) has been down for at least 2 weeks. If you have a radeon card, there's the rage3d tweak.
I wanted to get the latest version last week because I reinstalled my OS and I couldn't find it.
Honestly, I don't notice a difference. My monitor only supports 75hz at 1152*864 so I won't notice much of one. I guess I'm just used to it.
But I'm getting a new monitor soon and it will definitely come in handy.
EDIT- MeatGrinder - what' he's referring to is the "bug" in XP that doesn't allow for "optimal" settings of refresh rates. When you go to a game, XP automatically plays open GL based games at 60hz. Read the xp-refresh.net for info.