Hello.
I have the same problem.
I tried to use different skins but tabs in IE7 always look like this:

System Info:
WindowBlinds version : WindowBlinds 6.02 (build 43 x86)
WindowBlinds is installed correctly on this PC
WindowBlinds appears to be activated on this PC
Your machine supports per pixel borders on WindowBlinds skins.
(Plug and Play Monitor) 1 is attached to Intel(R) 82945G Express Chipset Family
Wblind.dll 2008/01/14 17:02:20
Wbsrv.dll 2008/01/14 17:02:10
Wbconfig.exe 2008/01/14 17:02:35
Wbload.exe 2007/09/27 17:47:44
Wbhelp.dll 2007/08/27 11:54:07
Wbui.dll 2007/11/06 10:13:05
Tray.dll 2007/09/12 17:58:21
Screen.exe 2008/01/14 17:02:18