Windows Media Player (WMP) has these settings to "arrange my music" as well as updating information about the files.
I wonder what you decided to set these to? Can you share this WITHOUT checking the control panels? I found most to be unaware of these settings and later ask about why files went missing or changed.
Also, if you are using the WMP server feature, that server would be the other user. Here's a note about that -> http://windows.microsoft.com/en-US/windows-vista/Sharing-media-on-a-network-using-Windows-Media-Player KEEP reading it and there's a link to turn it on and off.
My computer acts weird in my musics folder.-When I want to change the name of a folder the message comes up:This folder is shared with other peopleBut I know I never shared the file.In properties/sharaing tab/advansed sharing there is sharing permission for "everyone".Is it a security issue? My updated security software also can not detect anything. I scanned all files but I did not find anything.In security tab there are also two permissions for "WMPNetworkSvc" and "HomeUsers" and I dont know what they are. Are they safe?
I also see an unwanted and unfamiliar permission (sometimes not always) in permission list in security tab. The name of this permission is a string starts with s-1-5-21. The odd thing is that it disappear itself after 2 or 3 seconds.