SafeMSI is a simple free tool that starts the Windows Installer service, which is required for installing in Safe Mode in Windows 7 and Windows Vista.
By default, installing and uninstalling programs is disabled in Safe Mode in Windows 7. The reason for this is that, in Safe Mode, only a reduced set of services is running. This might cause problems with some installers, which is why the Windows Installer service isn’t running in Safe Mode.
On the other hand, installing and—in particular—uninstalling programs can fail because of interfering services. Thus, if you suspect that such interdependencies are the reason for installation problems, you can try running the setup program in Safe Mode. To start your Windows machine in Safe Mode, press F8 before Windows boots up.
Before you can start the Windows Installer service in Service Manager, you must first add the registry key MSIServer with the default value Service in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SafeBoot\Minimal\
Admittedly, this procedure is a bit longwinded. The free tool SafeMSI adds the registry key and starts the Windows Installer service. All you have to do is double-click the program. You can then install and uninstall in Safe Mode just like you are used to.
Note that the tool doesn’t allow you to remove the aforementioned registry key. You have to do this with the registry editor. However, it doesn’t hurt if you just leave the key as is because it is only effective in Safe Mode.