by Ken Task.
Am not a Windows person but assume most settings in my.cnf would apply across platforms.
Yes, safe to remove manually from moodledata/temp/backup/ but that should probably be last resort. There are three tables that track autobackups and a 'task' for cleaning up in moodlecode/admin/tool/task/cli/ or the Gui Admin interface. Those 'task' are run by cron so run your cron and get not only the files cleaned up but those tables tracking up to date with current/correct information. Might have to run cron several times to catch up.
Probably need to take care of the situation as soon as possible for the longer things fester the worse it could get.
'spirit of sharing', Ken