Are they grayed out?
When they are greyed out, that usually means either itunes or your windows user ID doesn't have permission to change them.
Check windows 7 permissions on the entire itunes folder, and all its subfolders.
Take full control & ownership as explained in this webpage:
Don't worry about the article's title being about how to delete files. Getting the permissions right is the same process and this is a pretty easy explanation.
Restart itunes so it will read the new permissions, and see if you can edit the song titles.