'Applying visual styles error'

I want to change the theme of my computer..
i.e.When right clicking on the desktop and clicking on properties the display properties box pops up..

Although when i try and change it to the Windows XP theme, it gives me this error 'the visual styles could not be applied'..

What am i supposed to do to sort this out? Please help!!

 

To try the easiest thing first, Click Here to open a Kelly's Korner page.

Scroll down to line 187 and in the right-hand column, click on "Restore Luna Theme" to download a zip file. You may have to right click it and left click "Save Target As" or, if using Firefox, "Save link as. "

Once you have it downloaded, unzip it to the C:\WINDOWS\Resources\Themes folder. Then see if things work in Display Properties.

Even if this is not the problem, it won't hurt to do it. All it does is replace a possibly damaged Luna theme folder with an undamaged copy.

 

Thanks so much!!!!!