Windows XP shows a file extension called .MACC but there is nothing in those files. What do .MACC files contain

MACC=media cache files

they store info that allows for quick scrubbing/preview without having to reread the MPEG file.

they can contain cfa .pek and .mpgindex files

you shouldn't delete MACC files unless you read more about them... let me know if this was of good help to you
--Cheers, IMberains