Is this during installation?
If so, as per this article, that can happen for a few reasons.
https://proconnect.intuit.com/community/help-articles/help/error-fatal-error-during-installation-160...
You might have to call into customer support tomorrow, but some questions might help narrow it down.
Do you get that error very first thing after running the installer, or at the end after you've gone through all the wizard screens?
Do you have plenty of disk space?
Are you installing from your downloads directory or from the CD drive, using a standard location (C:\ProWin32)? Or are you running from a shared drive, a thumb drive or something that might be considered out of the ordinary?
If possible a screen shot would help, as would emailing the files in C:\ProgramData\Intuit\ProSeries\Install\TY20\Logs to proseries_engineering@intuit.com.
