Ocean Life HD
Do you love marine life? Then this Windows 7 theme pack is for you. Ocean Life HD contains nine gorgeous high-definition images of aquatic life to grace your desktop. The theme sets your windows colors to a soothing aqua, but does not contain custom sounds (it uses Windows' Sonata).
To install the theme, just download and unzip the archive, then double-click the file; Windows takes care of the rest.
If you want something classy for your desktop, Ocean Life HD fits the bill.