Windows Installer will NOT start in Safe Mode on a Windows Server 2003 computer.

When you attempt to start Windows Installer in Safe Mode, you receive:
Error 1084: This service cannot be started in Safe Mode.

Solution:
To start Windows Installer in Safe Mode:
1. Restart your computer and press F8 before the Boot Menu or splash screen.
2. Open a CMD.EXE window.
3. Type the following commands and press Enter:
REG ADD "HKLM\SYSTEM\CurrentControlSet\Control\SafeBoot\Minimal\MSIServer" /VE /T REG_SZ /F /D "Service"net start msiserver
NOTE: You can use this technique to uninstall an application in Safe Mode.
NOTE: SafeMSI.exe freeware starts Windows Installer in Safe Mode on Windows Server 2003.
OR
1. Boot into Safe Mode.
2. Create the following registry key (it won't exist by default, so create this new key):HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Minimal\msiserver
(If you also want it available in Safe Mode w/ Networking, add the "msiserver" key under the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Network\ key found here as well)
3. Edit the "(Default)" value in the new "msiserver" registry key, and enter "Service" in the "Value Data" box. Click OK, and close the registry editor.
4. Reboot back into Safe Mode, and the Windows Installer service should now run and allow you to add or remove programs in Safe Mode.
If you STILL can't boot after uninstalling your product at this point, _THEN_ you might want to consider a repair install or a rebuild.