how do you check if a windows 7 version is a fake?

The reason I ask is because some of my classmates have told me that the Professional version of Win7 that is available through our campus ELMS website isn't really a "final version" and that it might start failing on March 2010. I have been holding off doing a clean install because of this and would like to see if me and a classmate can check for sure if it is a final version or not. Is there a file we could check? Is it "watermarked" in the wallpaper like the RC versions?

Thanks for the help.

Thanks a lot, I'll try that.