application/x-xpinstall

Hell,
       I have installed mozilla 1.7 and I am trying to install
calendar*.xpi from mozilla.org. When I click on "Install" it pops a
window which says

"The file calendar*.xpi is of type application/x-xpinstall (XPInstall,
Install ), Mozilla doesnt know of how to handle this file type" . What
to do with this file? Save/Open with any app??

Basically, I dont want to save it on to my HD and open/install it
using my browser itself, instead...I wanted to install it
automatically once I click on "Install" link. I had an entries in
xpinstall.whitelist.add in about:config. Please let me know of how to
install .xpi file using mozilla browser *automatically*. Thank you in
advance


-- 
Ravi Moka
Junior Sys Admin
Cassens Transport Co.,
Edwardsville, Illinois
USA - 62025