The left pane...?

That's actually a graphic which is found in your windows folder. Windowblinds won't touch it, so if you want to have it match your skin, you'll need to make one by yourself.
I can't remember the exact location of the graphic, but I'm sure someone else here can point out the location for you.

Check out http://www.virtual-plastic.net
You should be able to find more info on changing it over there.(Hope that link is right)

The left panels are configured with and HTML page located in your C:\Windows\Web folder.
The default file for almost all folders is called FOLDER.htt, but there are other ones such as NETHOOD.htt, MYCOMP.htt, etc.
Note that there could be other FOLDER.HTT files in certen specific folders such as C:\WINDOWS and C:\WINDOWS\SYSTEM and other special folders that have a different look.

If you know HTML you can modify those files to match your mood. Don't forget to make a backup of the origianl before you play with it.

Have fun!