Twice now I've had issues when auto-updating WACUP, the first time I just uninstalled it and did a fresh install of the new build, now it's happening again. It's worked fine on one PC, but on this one not so much. I'm a local admin (and the only user) on both machines and they're both running Windows 10 at the same patch level.
Basically it says that there's an access error trying to write to winamp.exe. Last time I renamed it and it went further, but complained about a couple of other files instead. It's installed in the default installation folder.