Acrosup64.dll Is Not Marked For Installation -

This is rarely a "virus" or a "corrupt OS." It is a version mismatch and ACL (Access Control List) conflict.

Here is the technical cascade:

In short: The installer sees a ghost. It knows the file should be there, but it has no instructions on what to do with it. acrosup64.dll is not marked for installation

acrosup64.dll is often loaded by the print spooler or a system tray app. This is rarely a "virus" or a "corrupt OS

Press Win + R, type regedit. Backup your registry first (File → Export). In short: The installer sees a ghost