Just as a footnote:
A 64-bit mIRC won't do anything helpful. mIRC is neither CPU nor data intensive, so it would not benefit from the two major 64bit features: 4gb+ memory space (mIRC certainly doesn't need that) and faster memory reads/copies (due to the ability to read/copy chunks 8bytes at a time rather than 4). Since mIRC doesn't need either of these improvements, I'd bet the only real benefit from a 64bit version would be not seeing "*32" in your process list.
