I have run into scenerios where I needed access to the Windows Installer service while in Safe Mode. You may be suprised to know that this service is not enabled by default. The following info will get it back for you:
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.