The “Not a valid Win32 application” issue can be caused by the below possibilities:
File is corrupt or incomplete.
Disc or hardware problem.
If the LegacySetup file is corrupt, incomplete or missing, Windows will be unable to execute the file and may generate this error message, or other messages.
Please download and save the LegacySetup.exe file to your Desktop by visiting https://legacyfamilytree.com/download-update.
Next, reboot your computer in Safe Mode; then logon to your computer as Administrator and install Legacy using the saved LegacySetup file.
Temporarily disable your Internet security (firewall, anti-virus, anti-spyware, anti-adware, popup blockers, etc.) as these programs can sometimes remove critical system files from Legacy.
We recommend that you use Internet Explorer or Microsoft Edge to download.
Disc or hardware problem:
If you're attempting to install a program and are getting this error, verify that the CD is clean. If the CD is dirty, scratched or bad, you could get this error during the install and/or get this error after the program has been installed because it was not copied properly onto the computer.
If you're still getting this error after carefully cleaning the CD, it's also possible that the CD-ROM drive or the drive you're installing the program from is not compatible with Windows or has drivers that are not compatible with Windows.
Download the latest drivers for your CD drive from the manufacturer's Web site.