If you are getting this error message on boot and cannot get into your computer, you probably have more damage to the operating system than you are going to like. You will probably have to recruit your local computer nerd to help you out with a problem like this.

You can try an SFC in the System config to find missing or corrupt DLL files and replace them (need your install CD). It is off the 'tools' menu and called 'system file checker' or something to that nature.