Here's the reply:
You can see this behavior in 2 cases.
If you install Popup Manager on a Win 98/ME machine and
then upgrade to
Win NT/2K/XP.
or
Sometimes the installer incorrectly identifies the OS you
are running. I
am working on a fix to the installer issue, but you can
run the installer
found here
http://www.endpopups.com/PopupManager_Unicode.exe to work
around the problem, it will not try to detect your OS and
will always
install the NT/2K/XP files.
I will also add something to my FAQ page to help other
users until I fix the installer.