So currently, I Have an i5 2400 and I was thinking of upgrading to an i7 2600k. If I do upgrade, would I have to buy another copy of Win 7? I've heard different things about this and was wondering if I could get a good answer.
No you won't have to get a new copy of windows, you won't have to even reinstall windows.
But I think you would be making a mistake on getting a i7, when Ivy Bridge is coming out very very soon.