Lost access to iTunes ("locked disk or do not have write permissions")

I clicked on my iTunes and received the message in the subject header...haven't made any changes recently or updated iTunes the only thing I can think of is that I recently logged into a website that asked me if I wanted to continue under my email address olive****@gmail.com (screen capture attached; I don't remember which site it was).



Looking at the capture with the administrators, why are there even three of them? It's my computer and I'm the only one who uses it, is there some way of unifying or eliminating two so I always have permission to everything? (All three are allowed to use iTunes as far as I can tell). Thanks.

64-bit Windows 10 Home version.