Window 8.1 LocalHost - XAMPP & UAC
I successfully loaded the latest XAMPP stack to my Windows 8.1 machine after receiving the same warnings shown below.
The UAC warning appears to have been related to Windows "assuming" the install was going to happen in the Windows software directory and not the usual c:\xampp directory.
I ignored the warning and made sure to install in the default C:\XAMPP directory. The installation was successful, however upon starting the XAMPP control panel I received warnings about the Apache and MySQL ports being blocked.
The PC is running McAfee security, so I went to
McAfee -> Firewall -> Ports & System Services, and placed a checkmark for HTTPS port 443 and HTTP port 80 to open them.
Restarted XAMPP control panel and everything works fine. No UAC issues...
Hope that helps.