I didn't think cpu bits had anything to do with file sizes, just ram. File size is typically dictated by filesystem. Also what version of mirc are you using, I believe some version before 6.35 (maybe the 6.1 or 6.2 series) had a 4gb max file size for dcc transfers. Pretty sure 6.35 doesn't and I know 7.xx doesn't.


http://scripting.pball.win
My personal site with some scripts I've released.