Updating can be daunting, see e.g.
Autodesk
What It Fixes:
- Corrupted registry keys on 64-bit operating systems
- Corrupted registry keys that control the update data
- Problems that prevent new programs from being installed
- Problems that prevent existing programs from being completely uninstalled or updated
- Problems that block you from uninstalling a program through Add or Remove Programs (or Programs and Features) in Control Panel