late last night I migrated from a MacBook to MacBook Air use an external hard drive. perhaps because I failed to click an option, I now cannot access the backups from before I migrated via Time Machine. as far as the MacBook Air knows, my history begins this morning, when I did my first back-up on the MacBook Air. I can access some files on the external drive, like applications, but a lot of the files, etc. have the little red minus marks on them. particularly vexing because the external hard drive has its space mostly filled up already, making it pretty wasteful of disk space. will Time Machine go back and erase that older data to make room? I hope my questions make sense.