Duplicate installations in Win7-64

after upgrading from 2.89A to 2.90A I now have two installations of the program, according to the Details panel of the executables:

2.89A under C>Program Files> mp3tag &
2.90A under C>Program Files (X86)>mp3tag

I'm surprised this happened, and also surprised that, since it did, that the positions of the two executables aren't reversed, since it is a 64 bit OS.

Can I delete the older version?

I also should have mentioned that Windows Control Panel only shows 2.90A.

Since only 2.90A shows up in the registry, I went ahead and deleted 2.89A with no ill effects (so far).

Perhaps your previous installtion was a protable one - which leaves no trace in the registry, so the MP3tag installation routine does not know anything about other installations.
If you delete the older installation including the data folder then you loose all your previously written actions and exports.