Install requires a system reboot?

First time I think I've seen that.

Can you please be more specific about the "requires"? Does it mean you're asked to reboot or that you need to reboot to reload the context menu shell extension?

It asks to reboot. The Explorer context menu extension still works without rebooting, although I haven't tested any of the changes.

Yes.

I've updated the version of the explorer shell extension which requires a reboot in case it's in use.

Bumping old thread, but I found it via search because I was having the same issue. So since I have a solution, I'll add it to this thread so that other might find it.

This still applies to the as of now current version 2.59a.

So the solution if you cannot reboot like me is simple, this worked for me: Do not choose to reboot, choose reboot manually later. Close all instances of Windows Explorer, except the shell process, no need to kill that one. Then re-install Mp3Tag, and there shouldn't be any request for reboot anymore at the end and the new version of the shell extension should be updated.