These are clearly false positives. I've downloaded mIRC 6.34 from multiple sites (FileHippo, OldApps, and Oldversion).

I have compared the MD5 checksum's and they all match.

Strange, that the antivirus software I've never heard of detected it (minus McAfee).

The current version, 7.19, it has "Open Candy" and that's a false positive - Read Here