Solution for Drive Not Reporting Full Capacity

This is usually an issue with 3TB or 4TB drives, as 2TB drives should have zero issues in Win7 (WinXP users might have to download a utility from the drive’s manufacturer to allow for a drive with 4K sectors). Out of the box these 3/4TB drives are typically MBR disks, which limits a partition to 2TB (actually, 1.8TB or so) relegating the rest to a separate partition.
If you want the full capacity in one partition, you need to convert the disk to GPT. To do this, type cmd at the Start search box; at the prompt type diskpart, then list disk, then select disk X (substituting X for your drive number), then convert GPT. Now go to Disk Management and create your massive single partition.