After googling for a while to try to see why I can't use my original Canon M as a webcam, I came across this forum, which is clearly an amazing resource. I have read all of the posts about clean overlays (and lots of others), and have tried (I think) everything: formatting SD as FAT 16, FAT 32, using both EOSCARD on Windows and MACBOOT on OS/X, adding the two properly-named files extend.m and script.req - and none of it works. I think the script simply doesn't run on my camera - I always get the overlays. It's apparently a DIGIC 5 processor and I have firmware 1.3, which looks like the most recent. Maybe it's just too primitive?
Should I just give up?