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Error
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I:\Games\Rayman Forever\RayKit\MAPPER.EXE



An error occurred while trying to rename a file in the destination directory:

MoveFile failed; code 2.

The system cannot find the file specified.



Click Retry to try again, Ignore to skip this file (not recommended), or Abort to cancel installation.
---------------------------
Abort Retry Ignore
---------------------------

If I ignore, then it just comes up with more files that cannot be found, including RAYRUN.EXE. I tried downloading twice, no luck either.
Any suggestions?

Maybe installation file is corrupted? Try redownloading the game again (via GOG downloader)
Or if you used downloader, try downloading via browser.

Disable your AV/Security software during the install. It's deleting/quarantining the files in the middle of the install.