im planning on reinstalling Win7 on a brand new HDD, i have heard that once installed and once you add\install your fav software applications (AntiVirus, DVD software etc etc...) you can create a so called "recovery DVD" or you can "Ghost" the HDD so it takes a snapshot of the clean and fresh installation.
This way, after months of use and loading the system with crap and other unnecessary software you can just pop that DVD in the CD-DOM drive and reinstall WIN7 again but already with the software you had in the beginning...
ahhh. i hope im making sense?