What's function of msgina.dll

When I go to Control Panel, User Accounts, Change the way users log on or off, I get an error message that says, "A recently installed program has disabled the Welcome screen and Fast User Switching.  To restore these features, you must uninstall the program.  The following file name might help you identify the program that made the change:  msgina.dll

 

The msgina.dll file is located in C:\Windows\System32 folder.  What would happen if I deleted this file?  Could deletion prevent boot up?

 

Thanks for the help!

ronglo