Registry Changes Don’t Stick

Hi All,
I have encountered a problem on a particular PC that is vexing me and thought maybe someone else may have seen this and knows the fix.

I have upgraded Netop Host software to a new version on this PC which changes/updates certain keys under HKLM Software, one of which is the product license code for the new version of Netop Host. The PC is running Windows 2000 SP4. When I reboot the PC those updated registry keys revert back to what they were prior to the upgrade and the new version of Netop Host fails to run.

I have tried uninstalling/reinstalling, manually updating the registry keys, I have checked the registry permissions. All appears in order till I reboot then the changes are lost. Anybody have any ideas?