I don't receive any error messages. I just noticed that the error log was being produced with an "Unknown version of Windows" message. I never noticed that file being created before so maybe the problem is with me not noticing that file being created before now.
(I just thought an error log would only be created if there was an actual error & Windows 7 has been out long enough that Mp3tag should recognize the reported OS being Windows 7 as not being an error.)
OK, so it's not an error. The log file is created on each startup since the very first release of Mp3tag and is not due to Windows 7 not being detected.
But you're right: Windows 7 should be reported as such and I'll change that to the next release.