Hi,
I installed a program on my mac that helps offset RSI. Basically, it forces you to take short breaks at an interval you set up. So, I set up mine to do a 30 second break every 10 minutes and a 5 minute break every hour. The 30 second breaks are great for stretching your hands and wrists, moving them in different directions than just around the mouse.
During the 5 minute break, I stand up and do full body stretches.
This really helps to keep your muscles from conforming to the mouse and the chair and lowering the risk of RSI.
Like I said, I am using a program for Mac:
AntiRSI - TECH.inhelsinki.nl
You might do a search for something for Windows. Here's something I found with a quick search:
Download of the Day: WorkRave (Windows/Linux)
You'd be surprised (or maybe you wouldn't) about how fast an hour flies by if you are into a project. These types of programs are great for ensuring you take a break.
Eric