Symptoms

When you install FineReader Engine on a machine where the previous build has been installed, you might face the exception "The path is not of a legal form."

Cause

This issue may occur because the old build was not completely removed before installation.

Resolution

There are a few steps to fix this:

1. Make a backup copy of the Windows Registry following the official instructions from the How to back up and restore the registry in Windows article. 
2. Check and remove all unnecessary entities. Computer\HKEY_CURRENT_USER\SOFTWARE\ABBYY\SDK\12\Installations\
3. Unregister FREngine.dll manually using the following command:
   

   regsvr32.exe /u "<path to FREngine.dll>"

   And register it once again with:

   regsvr32 /s /n /i:"<path to the Inc folder>" "<path to FREngine.dll>"