ITNinja

This is the local MSI repository for your computer, where MSI, MST and MSP files are cached for local use (for example, it may be used for uninstall and repair functions without going to the network.)
They are named in a random way, which makes knowing what application it is associated with a real pain. If you have Windows 2000 or Windows XP try this:
In Windows File Explorer, click "View" from the tool bar and select "Choose Columns". From the list of available columns, check the box for "Title" and press "OK". You may need to scroll to the right, but there should now be a new column that contains the title for the MSI (which, in most cases, should be the name of the application it installed.)
If you only have a few files to scan, simply hovering the mouse pointer for a few seconds over any msi file in the installer directory will display tooltip containing the property information.
Sometimes these files can take up some space, and I have received questions about what the harm would be in removing them. First off, this is where all your Windows Installer shortcuts point so at a minimum you may loose icons in each respective shortcut on your desktop/start menu. Secondly, uninstalls will be unable to restore old files and such failures may make it impossible to properly uninstall these applications. Bottom line: this is not recommended! If space is an issue, consider removing any software not being used. Deleting these files is a recipe for trouble and could mean a complete reinstall of Windows to recover.