I have stolen this from xlii.com - even though it is about 6 months old it is worth repeating here. Due credit goes to the original author, Hollwood :D
This is for those of us running 2K / XP and have an nVIDIA based graphics adapter:
I went to VIAARENA lately looking for a solution to the 2k/XP/nVIDIA refresh-rate problem. The answer is nothing short of AWSOME. Enter NVRefreshTool, a simple 600k program that lets you manually adjust and set the refresh-rate for ALL resolutions. Never be hampered by crappy 60Hz refresh-rates again!
Download it HERE , and follow these simple steps.
1. Make sure your monitors PROPER drivers are installed.
2. Install NVRefreshTool
3. Open up your ADVANCED ADAPTER PROPERTIES...you know..the place you adjust your refresh rate.
4. Click the "ALL MODES" button
5. In NVRefreshTool for each resolution, input the maximum refresh value displayed in the ALL MODES window.
6. Apply the settings, reboot and PRESTO! Your gaming at your max refresh every time, every resolution!
7. note : If you change drivers, you need to remove/reinstall/re-setup NVRefreshTool.
8. Your welcome
REFORCE works a treat too. :)
But dont ask me where you get it, just search.