Vista not only elevates installer's process rights (UAC), but makes it running from administrator. This way installer forgets about logged user and executes installer as it was started by admin. Thread with the same problem
http://forums.winamp.com/showthread....hreadid=265780
May be Vista SDK can help with process token tricks (new NSIS plug-in required), but SDK "Download Size: 1 KB - 1185.7 MB*" :-(
http://www.microsoft.com/downloads/d...displaylang=en