Been stuck with some software and can only boot into safe mode. You think to yourself, "OK, let me just uninstall the offensive program"...only you realize that you can't because it is based on an MSI installer package. Safe Mode restricts the services that can start and this includes the Microsoft Installer Service. But...there is a workaround via a registry edit. Be careful as always, break the registry, and you might just break Windows for good. Step by step below...

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.