If you are running any other programs that would customize the toolbar (or task pane), I would suggest unloading it to start.
I would further suggest the following:
1 - Use WB configuration to select and apply the "Windows Classic" theme
2 - Unload WB
3 - Restore all icons to the XP default
4 - Reboot the computer
5 - Restore the XP default "Luna" theme via the Display Properties\Themes tab\Theme drop-down list.
6 - Start WindowBlinds and select one of the skins that came with the program (say - 5imple alpha, or DogmaX), but do not apply it yet.
7 - Go to the Toolbars section and select the "Always use the toolbar icons defined in the current skin" option, and then click the "Apply Changes" link on the left side of panel.
8 - Once the skin is applied, reboot the machine and then check for toolbar icon changes.
Note - this assumes you are running the full version of WindowBlinds.