These questions are highlighted automatically due to the tags you've frequented. There's no way to turn it off that I know of. Perhaps this should be a feature-request unless I've just missed it. This was put in a few months back IIRC.
You can manually add a tag to your favorites (and thus have it highlighted) by typing it into the "favorite tags" box on the right side of the home page. It's possible that you could remove Windows 7 from your favorites by adding it manually and then removing it, but I'm not sure.
