I downloaded some soundpack themes from this site but I don't know how or where to install them. They don't seem to be similar to the sound files in Windows Media folder and I'm unable to play them.
If you are talking about sound themes that you can download from the WinCustomize Galleries you will need SoundPackager. Here is a link to the product page.
https://www.stardock.com/products/soundpackager/
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