It writes to the registry at:
HKEY_CURRENT_USER\Software\MiKTeX.org\MiKTeX\2.9
HKEY_CURRENT_USER\Software\MiKTeX.org\MiKTeX
Plus the usual Trolltech entry.
It also created YAP.ini in C:\WINDOWS
Can someone run it from a removable device and test for portability? Thanks.The portable edition allows you to run MiKTeX from a portable storage device