It's come to this: You fire up Vista's Computer window and see that your boot partition—the hard drive section on which Vista resides—is running out of space. You spend a few hours getting rid of as much fluff as you can, but a week or so later, the free space is disappearing once more and Vista warns you (with a red bar under the drive name) that you have a problem. What to do?

If your hard drive has only one partition—meaning that your entire hard drive really is filled up—there's nothing you can do but buy a new drive and transfer files over to it. Of course, you could just reinstall Vista on the new drive and start all over, but that's a huge job. If you have more than one partition on your boot drive, though, you might be able to salvage the situation. And just for fun, let's say you don't have third-party partition management software available and want to avoid spending money if you can. While Vista doesn't have comprehensive partition management capabilities, it will give you some help.

To work with your drives in Vista, open the Disk Management console tool. The easy-to-remember way is to click Start, right-click Computer, and choose Manage, yielding the Microsoft Management Console (MMC). The slightly more direct way is to type diskmgmt.msc in the Search field at the bottom of the Start menu; this time you get only the Disk Management console tool. We'll work with this one here.

In both these screenshots, the current Vista boot partition—ATA160-Partition2 (C:)—is selected; the diagonal lines highlighting the partition show the selection. As you can see, this 160GB drive (known as Disk 1 to the system) has three partitions, respectively 65.06GB, 68.08GB, and 19.53GB in size. But 68.08GB is proving a bit too cramped for the boot drive, mainly because Vista, like all Windows versions, expands as you use it and add to it; adding some space would be useful.

If you've selected the Tile view, opening Computer in Windows Explorer will show you the space used by each drive on your computer. Here we see the three partitions of Disk 1 highlighted. The boot drive, C:, has 21.3GB free, while D: has 15.1GB and S: has 18.5GB. The obvious solution is to make use of the barely used S: partition, and that's what we'll be doing here.

Really, it would seem equally obvious to make use of the 15.1 gigs of free space on D:, possibly even clearing off more space by deleting a bunch of unused folders on that drive. But using D:— the partition labeled ATA160 and showing immediately to the left of the boot partition in the Disk Management console—is actually an extremely bad idea. Here's why: The Vista boot manager (like that of earlier Windows versions) needs to know precisely where on the hard drive the boot partition is located. When you install Vista, it records this location information and lives by it; if you change where the boot partition starts on the hard drive, the boot manager won't be able to find it, and Vista won't load. So do not, under any circumstances, expand the Vista boot partition by incorporating space available on a partition to its left (as shown on the Disk Management console tool)—you may, however, freely use space on a partition immediately to its right. In this particular case, partition ATA160 (D:) is off-limits, but partition ATA160-Partition3 (S:) is ours for the asking.

By far the easiest way to grow the boot partition here is to get rid of ATA160-Partition3 (S:) completely. That will make the entire space available for C: to use. To do this, first use Windows Explorer to copy or move all the data on S: to another partition. When finished, right-click S: in the Disk Management console tool and choose Delete Volume. This will get rid of all data on the drive and unpartition it so that it becomes what Vista calls "unallocated" space.

If you don't want to delete S: entirely, you can shrink it, preserving the data that's already on it. Right-click the partition in the Disk Management console tool and choose Shrink Volume.

The resulting dialog defaults to shrinking the volume to roughly half the size, or (if the partition is more than half full) a few megabytes greater than the amount of data already on it. Adjust the amount of space to shrink, if you wish, but usually the default works fine. Click Shrink and you'll see the results shown in the next screenshot: ATA-Partition3 (S:) is still there, but the drive now has a 9.72GB section of unallocated space.

—Next: Creating a New Partition

Now for the fiddly part. Because the unallocated space isn't directly adjacent to the boot partition, you can't use that space to grow C:. Instead, you need to transfer everything from S: to the currently unallocated space and then delete volume S:. First, right-click the unallocated space and choose New Simple Volume. The New Simple Volume wizard steps you through the process, giving you a default new volume size equal to the available space (the default is fine).

In the next dialog of the wizard, you can assign the new space any drive letter you wish, but again the default is usually the best bet. Finally, the wizard asks you how to format the partition: Stick with the default NTFS file system and default unit size, but give it a new label (you can do this later as well) and, to save you a great deal of time, check the option to perform a quick format. Click Next and then Finish. You now have a new partition ready to go.

Transfer the data from S: to the new partition. When the transfer is complete, right-click S: (which you no longer need) and choose Delete Volume. An error message will tell you it's currently in use, but since you've already saved what you need from it, go ahead and perform the deletion. You now have the unallocated section immediately to the right of the boot partition, exactly where you need it.

Whichever of the two methods you've used so far (claiming all of S:'s original space or only a portion of it), the next step is the same. In the Disk Management console, right-click the boot partition—ATA160-Paritition2 (C:) in this case—and choose Extend Volume. In the resulting Extend Volume wizard, click Next to move to the Select Disks dialog, where again the default selection is usually entirely appropriate.

Click Next and then Finish. As you'll see, the boot partition has added the unallocated space to its total, allowing Vista to grow to accommodate future upgrades and installations. The final step is to reboot your machine to ensure that it actually works, getting ready to use your ghosted system in case something has gone wrong. Assuming it hasn't—and it really shouldn't have—congratulations! You now have a larger Vista boot drive.