I have a 1 TB HDD which I am running from an external dock. it doesn't show up in windows explorer, so I checked it with third party software (a partition manager) and it shows up as unallocated space, but it won't let me make any changes to it. No formatting or anything. The program says that the MBR needs to be fixed. how can I do that. There isn't any data on the HDD that isn't backed up so it's ok if I need to format it.