I just downloaded a themes package for my computer, after making sure that it was virus free i then tried to install the files, everything extracted well but then when i tried to pick the theme as my current one it gave me a error message, something about a missing file, did i install it incorrectly or something?

It does not really matter if we know about themes - it sounds as if the download was corrupted. Either that or the download you have is not for your version of Windows.

If you're using Windows XP you cannot use unsigned themes (90% of the themes available on the Internet) without patching the uxtheme.dll file. Once you've done that, you can use themes or ms-styles as they're more commonly called.

I have no idea how it works with Vista.

If you want help with an error problem, this won't cut it- " error message, something about a missing file, did i install it incorrectly or something?"

What is 'something'- twice?

I got the error figured out and it's all taken care of, i was just insalling it to the wrong folder