You can try the following steps:
1.) Start the old existing v3.17 Mp3tag manually
2.) Create a backup from your v3.17 configuration, according to the mentioned notes from inside Mp3tag v3.17 and File -> Save configuration
3.) Re-Install v3.17 32bit-Mp3tag "over" your existing v3.17 32bit-Mp3tag -> this should create a deinstallation entry in your control panel and Start menu
4.) De-Install v3.17 32bit-Mp3tag
5.) Re-Install v3.18 64bit-Mp3tag