I've got a 500 gig external harddrive that I have partitioned into two drives. One is for all my misc stuff and one is for my Time Machine backup. For some reason, lately my Time Machine partition will not mount on my computer but the other will. I get a "B-Tree" error every time I try to repair the partition so I just want to wipe it and do a clean backup. If I select just that partition of the drive in Disk Utility and select to erase it, will it erase the entire external drive, including the other partition? Let me know if I need to explain further. Thanks everyone.