Windows XP uses a new interface (much better looking too, in my opinion). This setting allows Search Bar Pro to take advantage of the new visual style. However, there are some problems with programs written in Visual Basic. I have been able to work around all the problems except one, and that is some flickering in certain windows when moving the mouse. I think the new visual styles improve the look of Search Bar Pro dramatically and it is worth the small amount of flickering. But I'm a good programmer and realize what I think is best isn't necessarily best for everyone so you have the option of disabling it.
Note that this setting is only available to users running Windows XP. Users running any other version of Windows won't even see this setting.
If you change this setting, you will have to restart Search Bar Pro before the change will take effect.
This what Search Bar Pro looks like with this setting enabled.
This what Search Bar Pro looks like with this setting disabled.