Is it possible to downgrade Windows 8 Enterprise to a Windows 8 Pro? If so, do I keep the settings (such as the Proxy Settings on the Control Panel) or do I need to reinstall my (non-metro) apps?
Yes it is; it just takes a little time (it is worth it)
- Open registry editor (run
regedit.exe) and navigate to HKEY_LOCAL_MACHINE→SOFTWARE→Microsoft→Windows NT→CurrentVersion
- Double click on
ProductNameand change to "Windows 8 Professional".
- Double click
EditionIDand change to "Professional":
- Now navigate to HKEY_LOCAL_MACHINE→SOFTWARE→WOW6432Node→Microsoft→ Windows NT→ CurrentVersion
- Do the same as you did in steps 2 and 3.
- Close regedit (You don't have to restart your computer).
- Close and insert Windows 8 Pro CD and install.
Editor's note: Somebody who didn't have commenting privileges tried to edit this answer with the addendum "You do need the install files and a product key for Windows 8.1 Pro."