hi,,, from what i can find out this is a file type for Win98rk (windows 98 resource kit)http://en.wikipedia.org/wiki/Resource_Kit
apparently its a microsoft program you can get for windows 98.
are you running win 98 ?????
did you mean MSI files maybe ???http://chris.pirillo.com/what-is-msi/
hope this helps,,,, as to weather you can bin them or not, well thats up to you,,,, google for it and see what comes up,,, but if its not broke then dont fix it as they say,,,, if there not eating up hdd space then dont worry