When I right click on every file, there is a take ownership button. I'm sure it is not there yesterday. I tried clicking it and don't really notice anything happening.
If you put a second drive in your PC from an old build, where you used a different account/password combination than your current system, that option allows you to "take ownership" of those files and access them. If you search on here for the phrase "take ownership" you'll have more info than you'd ever care to read through.
and also in some articles which have been published in a 'Windows Vista' magazine in the US. Perhaps somebody has read about it there, or somewhere else, and then followed the instructions to get it added to your Vista installation. It wouldn't have appeared there by 'magic'.