Huh, didn't know WinRAR pops up a UAC prompt. You never stop learning. :-)
Ok, in that case it sounds like a virus scanner issue. xmplay.exe is a packed executable and these are often used by malicious software, too, so this must be a false positive. I'd suggest checking your antivirus package for any activity - maybe disable it for testing. Also see if MS Defender is still running (even though it shouldn't if it detects another antivirus).