Windows 7 upgrade from... Windows 7?

I've been running the evaluation copy of Windows 7 but now that I'm ready, I want to buy the ultimate full version. I know I'll need the full version, not the update. However, will I have to reinstall everything? Does it wipe my hard drive before I do it or will the download detect im running windows 7 already and just "update" me off of what i've already installed?

i guess the next question is what's the best way to back everything up (data and documents mainly).

Really easy to back up
Use Windows easy transfer. You can download from the Microsoft Site. Just follow the easy instructions. Be aware, it will transfer almost everything except programs. Those you must use the original installation disc. If you, previously, made a copy of your hard drive you can transfer back to your hard drive.

hacku said:

You don't need the full version. You can save yourself $100 by purchasing the Upgrade which will still do a full install of the OS...

Yup, see here: http://www.winsupersite.com/win7/cle...rade_media.asp