Why can’t I ac­cess my 4TB hard drive’s full ca­pac­ity?

Computer Active (UK) - - Problems Solved -

QI’ve up­graded my Win­dows 7 PC with a 4TB hard drive. My 1.5TB and 2TB drives al­ready work, but I can only ac­cess 2.2TB of my new 4TB drive. All three are NTFS for­mat­ted, and I’ve checked the drive’s par­ti­tion scheme. Can you help? Paul Finch

AWe think the 4TB drive is con­fig­ured as a mas­ter boot record ( MBR) drive, which ad­dresses sec­tors of the drive us­ing 32bit num­bers, giv­ing a max­i­mum of 232 sec­tors. Each has a ca­pac­ity of 512 bytes, giv­ing a rough to­tal of 2.2TB.

You need to con­vert the drive to the GUID Par­ti­tion Ta­ble ( GPT) for­mat, which uses 64bit num­ber­ing. First, back up the drive, then use Disk Man­ager to delete its par­ti­tions and vol­umes un­til it shows only Unal­lo­cated. Right-click the ‘disk in­for­ma­tion’ tile (to the left of the bar where you deleted the par­ti­tions) and the GPT con­ver­sion should be avail­able. Now you can re-cre­ate the par­ti­tion(s) and copy your data back on.

But be­cause your mother­board has a con­ven­tional BIOS, rather than the newer UEFI type, your PC won’t boot if you have Win­dows in­stalled on the 4TB drive. You’ll need to in­stall it on one of the other drives, or use cloning soft­ware to move the contents. This will over­write what’s on the smaller drive, so back it up.

Af­ter do­ing this you prob­a­bly can’t delete all the ex­ist­ing par­ti­tions on the 4TB drive and won’t be able to con­vert it to GPT. Solve this by run­ning Diskpart in Com­mand Prompt (the same tool we rec­om­mend Trevor Moore uses on page 65).

Type diskpart, press En­ter, then type list disk and press En­ter. Now type se­lect disk X, where X is the num­ber of your 4TB drive as dis­played by list disk. When Diskpart con­firms the drive has been se­lected, type clean, press En­ter, and you should see ‘Diskpart suc­ceeded in clean­ing the disk’. Disk Man­ager should now show that the drive is empty and can be con­verted to GPT.

You need to empty a hard drive be­fore you can con­vert it to GPT

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