Windows 7 - Nothing happens with "only black" theme. why?

I have among others the "only black" theme. I have the folder, and the .theme file in the default user/..../themes folder.
but when I click on it, nothing happens.
why?

also, does it actually matter where the particular theme folder lives? seems to not, as it was in XP..

The theme folder and the .theme file go in C:\Windows\Resources\Themes folder.
Jerry

i see what's up now.. I had tweaked some parameters for performance that nixed the visual styles... interesting that in Windows 7 "themes" are still referred to as 'themes' but in the advanced properties there is no checkbox for themes as before... just individual components of themes, and no error message to say why your theme does not activate!
a novice would be quite confused about all this.
no wonder some of my customers get hopping mad at their shiny new Windows 7 laptops, then I find out that its mostly about appearance/visual/personalization issues...

Good to hear you got it figured out.
Jerry