Windows Can't See All of a 400GB Disk: What to Do?

Reader Eric writes: I recently installed a Seagate 400GB hard drive into my existing computer. However, Windows XP is only showing it as a 127GB drive. What would cause this to happen, and how can it be corrected?

This is a problem that dates back to both PC and Windows architecture limiting the size of certain storage elements. Windows 95 could not access disks larger than 32GB, for example. That's because at the time Windows 95 was developed, the state-of-the-art hard drives were about 1GB (or smaller). Seagate's 2.9GB drive cost nearly $3,000. Microsoft didn't really envision anyone developing 32GB drives in the foreseeable future, and it was (mostly) right: The industry didn't hit 32GB until the year 2000.

Now you're seeing a similar limitation, as Windows XP (without service packs) has a maximum capacity as well: 128GB (formatted). However beginning with Service Pack 1, XP enabled the use of larger-capacity drives, so that's your first step: Run Windows Update to make sure you have your system completely up to date. I suspect this is already the case, though, so you'll want to move on to the next step. Essentially, your registry could still be limiting large drives incorrectly, and you need to give it a tweak.