Failsafe MSI (FSMSI)
http://patrickmylund.com/projects/fsmsi/

Failsafe MSI (FSMSI) is a Windows shell script that enables and starts the
Windows Installer service in fail safe mode. This is particularly useful
for removing applications that are preventing normal system startup but
still require the MSI service to be running to be properly uninstalled.

Usage:
  To enable:  fsmsi.cmd
  To disable: fsmsi.cmd deactivate