Windows Installer

Hello,
I am having a major issue with a server we have. Currently we are running NT 4 Server and for no reason everytime we try to install something we get:

“The Windows Installer Service could not be accessed. This can occur if you are running Windows in safe mode, or if the Windows Installer is not correctly installed. Contact your support personnell for assistance:

How can we fix this issue without upgrading or reloading?