Because we keep getting asked for it, here is the Winamp5 Classic base skin in all it's 32bit glory
Read this thread for tips on making Winamp Classic Skins.
How to make Winamp classic skins like a pro
For details on how to convert your skin from .zip to .wsz etc etc, read this thread
How to convert .zip files to Winamp skin files
Attached Winamp5.51 Classic base skin, 3rd December 2007