I use windows Vista but can't find the themes folder. In Vista there is no documents and settings/users, there is C/users/documents. I can't find a themes folder anywere in the system. Where do I put the skins for Limewire?

Try here: C:\Users\your username\AppData\Roaming\LimeWire\Themes

You'll need to show hidden files & folders to be able to find that Themes folder, the thread below explains how to do that.
LimeWire Pref Folder in Vista

Thanks a lot. I had to look but I found out. I installed a few skins, saved the skins as lwtp files and restarted Limewire. It's working just fine. Thanks.