Failed uninstall and re-install of WSUS 3.0

I cannot uninstall WSUS 3.0 64bit and getting many failure messages. The first error that I got was using Add/Remove programs removed that told me a failure to complete the un-install, but removed it from the Add/Remove Programs list! After that when I used the command-line /u parameter then it also failed every time. Below are the four error lines that always occurred:
2007-06-19 16:50:08 Error MWUSSetup RemoveWsus: MWUS Uninstall Failed (Error 0x80070645: This action is only valid for products that are currently installed.)
2007-06-19 16:50:08 Error MWUSSetup Wsus MSI uninstallation failed. (Error 0x80070645: This action is only valid for products that are currently installed.)
2007-06-19 16:50:08 Error MWUSSetup CSetupDriver::LaunchSetup:
Setup failed (Error 0x80070645: This action is only valid for products that are currently installed.)
2007-06-19 16:50:09 Error MWUSSetup DoInstall: Wsus setup failed (Error 0x80070645: This action is only valid for products that are currently installed.)

Is there any solution for this failure messages? Thanks

I think that you are not suppoed to delete the regkeys manually since they are used for uninstall. Are you able to still carry the earlier logs to show why first uninstall failed? The logs that you can find will be under %temp%\wsussetup*.log.

Thanks for the reply showing how to edit the registry. It was the last hope because WSUS does not seem to fall under Microsoft support services and their recommendation was to rebuild the server. Also, I dont have the old %temp%\*.log files. So, can you tell me how to force install WSUS 3.0 again?

You should first of all not use the MSI cleanup tool to unblock the issue. You can try to install WSUS on another test machine and then import the WSUS regkey from there to your original machine at HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Update Services and then do another uninstallation. But the regkey values may not necessary be an exact clone to your original setting, depending on how you choose to install in the second machine.