I'm using this theme: [Only registered and activated users can see links. ]

As you can see in the screenshots as well, the search bar's text background is still white. I'm looking for a program that can make modifications to Classic Windows 7 themes, is there one? Also, I'd like to make other changes to this theme as well. I thought about changing stuff using Resource Hacker, but I'd have to know the IDs of everything that's in the .theme file itself, and I'm not even sure that would work with a classic theme.

What program/editor is capable of this?