Rather than fiddling around with:
- uninstalling old programs,
- worrying about registry bloat,
- wiping and reinstalling,
- re-entering your license key
- re-activating your Windows operating system
consider ghosting your partition/drive once you get everything installed. Don't go through the unnecessary pain again of downloading the patches (etc) twice a year.
Make yourself a ghost image with the OS as you'd like to be able to have it again as. Heck, make a few images of all kinds of OS installs and application versions!
Keep that ghost image on hand, and when you feel it a bit sluggish, just reimage your machine from the ghost image. Yes, there will be more security fixes since the image's creation. When that does happen, consider re-creating a new ghost image of the newly patched system, in preparation for 6 months down the road when you know it's going to feel sluggish.
Regarding newer versions of browsers, etc.: perhaps those volatile apps shouldn't be installed in your image. Save those for a batch file that you can run to help automate your install of apps in your new shiny OS after you've wiped over.