[X4U] Problem with downloaded files

[eleventhvolume]

I'm having an intermittent problem with certain downloaded files. Via
MacWorld (http://www.macworld.com/weblogs/macgems/) I obtained a small app
that puts up a dialogue box to prevent accidental quitting of Safari (very
useful!). I decompressed the zipped file and now have a folder inside which
is a 'Packages' folder and an 'install taboo.mpkg' file which has a blank
icon. Double clicking the .mpkg file opens a dialogue box asking me to
choose an application. What application should I choose or what should I
change to enable me to install this? Many thanks for any help you can give.

All the best, Colin.