I can't mount a USB 3 hard drive on either of my two macs. One is 10.7.5 and the other is 10.8.2. The drive is ExFAT formatted with a Master Boot Record (MBR). It mounts just fine on a Windows 7 PC, where it was formatted. I have another ExFAT MBR drive that works on all computers. Attached is a screenshot from Disk Utility, and this is what System Profiler says: Code: Capacity: 1.5 TB (1,500,301,909,504 bytes) Removable Media: Yes Detachable Drive: Yes BSD Name: disk6 Product ID: 0x2320 Vendor ID: 0x0bc2 (Seagate LLC) Version: 1.00 Serial Number: NA4G2DVT Speed: Up to 480 Mb/sec Manufacturer: Seagate Location ID: 0x05100000 / 2 Current Available (mA): 500 Current Required (mA): 36 Partition Map Type: MBR (Master Boot Record) S.M.A.R.T. status: Not Supported Volumes: Dickhute: Capacity: 1.5 TB (1,500,298,346,496 bytes) File System: ExFAT BSD Name: disk6s1 Content: Windows_NTFS Volume UUID: 239B8B0D-222B-3B50-B147-FAC9ABFAFECB Anyone know how to fix this in Mac OS X? It's interesting that the Content descriptor is Windows_NTFS. The drive is a Seagate Expansion Portable.