msi extensions files turned into unknown application.

[Guest]

..msi extensions files turned into unknown application.Seems to be i have
deleted.how do i recover back

my english is a bit rubbish.Bare with me.

...............i want emergency help........... .
msi extensions files turned into unknown application.
i run XP sp2.
when i was in cmd promt it got changed.....
i was exploring command in DOS commands. i was trying to view particular
extension files only using DIR command.
when i using ALLOC command my .msi extension get deleted.
Any one who is GOOD IN DOS COMMANDS HELP ME.
or
say me the alter native way to open " .msi " files

 

[JS]

How to re-install Windows Installer:
http://xphelpandsupport.mvps.org/how_do_i_reinstall_the_windows_i.htm

Also:
Common Windows Installer Problems
http://support.microsoft.com/?kbid=555175

JS

 

[Peter Foldes]

What is the name of the unknown extension.