New
#31
You can do a clean install of Win7 on a bare hard drive using only an upgrade version:
Clean Install with a Upgrade Windows 7 Version
If you don't have a qualifying older OS on hand, you'd be in violation of the EULA (end user license agreement). That would be between you and your conscience, though; as far as I know, there is no mechanism in Windows to prevent it.
It'd be easier to use a generic "system builder" version, although apparently you aren't really supposed to do that, either. (That license is intended for PCs built for sale, not for home users.)
The student version is the best deal, if you can qualify for it.