Hi,
While either method should work (an "over-the-top" install or a clean install), we recommend using a clean install to upgrade to the 4.0 release.
Clean Install Instructions:
1. Open SpywareBlaster and press the "Disable All Protection" link under "Quick Tasks".
2. Close SpywareBlaster.
3. Go to Add/Remove Programs and uninstall the entry named "SpywareBlaster v3.5.1"
4. Download the latest SpywareBlaster installer from
http://www.javacoolsoftware.com/sbdownload.html
5. Install the new version, and enjoy!
Best regards,
-Javacool