How do I change the background on Sidebar?

[Guest]

When I first set up my new PC and Vista, the sidebar was transparent. Now
that I've set up a few other things, I have just a plain grey background on
the sidebar. Is there some way to reset it to transparent or change the
background?

 

[Lilo Lentz]

Could be your windows Theme has reverted back to basic instead of Aero.

 

[Guest]

When I first set up my new PC and Vista, the sidebar was transparent. Now
that I've set up a few other things, I have just a plain grey background on
the sidebar. Is there some way to reset it to transparent or change the
background?

I have the same problem using Windows Vista Basic and in addition my new
style start button has changed to one that has the new round windows symbol
but also says "start". I cannot find any settings to change to get this back
to how it was originally. Any help please?