Research the discussions at http://groups.google.com/groups?q=MRUN32.INI but the bottom line is that its very likely some MALWARE which has been removed left a treasure behind.
It will take time for me to read the passages to see if the culprit was noted.
You start reading too.
Bob
Ok, I've got serious problems. What ever this file is, it is now missing. Since my cable installer put Spybot on my computer, I'm having problems reaching web pages that I've always gone to. Now my disk defrag and thorough scan disk don't work either. I've cleared out my cache, internet history, shut off my active desktop. I don't know what else to do. The web pages I can't get to say HTTP 500 internal server error. Is the missing file part of the reason? I'm using windows ME and internet explorer 6.0 with the update SP. HELP?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic