Basic disks, used in Windows 9x and NT, are used by default in Windows 2000 and Windows XP. They may contain up to four primary partitions, or three primary partitions and one extended partition with unlimited logical drives. Primary partitions and logical drives that exist on a basic disk are known as basic partitions. Dynamic disks, originally introduced in Windows 2000 and supported in XP, are physical hard disks that contain dynamic volumes. They’re designed to give you some flexibility that you just don’t have with basic disks. For example, with a dynamic disk, you may extend a partition even if no contiguous space remains on the disk. If no free space is available on the disk, you may even extend the partition onto another dynamic disk.

Because with dynamic disks, you can extend a partition anywhere new space physically exists, as long as it’s on a dynamic disk in your system, you also enjoy the benefit of fault tolerance. The dynamic disk format obviously offers significant advantages. Here, I’ll cover a few caveats you should be aware of before making the leap to dynamic disks with Windows XP and then show you how to make the conversion.

Criteria for dynamic disk conversion
One of the most important facts to know before you perform the conversion is that the conversion is a one-way process. It’s easy to convert a basic disk to a dynamic disk. However, you can’t convert a dynamic disk to a basic disk unless no partitions exist on the disk. Therefore, if you want to convert your disk back to basic, you’ll have to back up all of your data, delete the partitions, convert the disk to a basic disk, create your partitions, and restore your data. Since this is a lot of work, make sure that you really want to convert your disks to dynamic disks before doing so.

Remember that any existing primary partitions or logical drives will be converted to volumes. This means that you shouldn’t convert a basic disk to a dynamic disk if you upgraded from another operating system to Windows XP and are considering uninstalling Windows XP to revert to the previous operating system. Once you’ve converted your basic disks to dynamic disks, reverting to the previous operating system becomes impossible. Windows XP Home Edition, Windows NT, Windows 98, and Windows Me don’t support dynamic disks.

You should also avoid using dynamic disks if you’re running a multiboot environment. Even if you’re multibooting between Windows 2000 and Windows XP or between multiple copies of Windows XP, avoid using dynamic disks because Windows uses the registry to keep track of the dynamic disk databases. Since each copy of Windows has its own registry, only the copy of Windows that you used to convert the disk would have the appropriate registry entries. This may cause the dynamic disks to be inaccessible to the other copies of Windows.

A hard disk may contain partitions created by other operating systems. For example, a hard disk might contain a Linux or an OEM partition. You shouldn’t convert such hard disks to dynamic because the foreign partitions become unreadable to their respective OSs.

Windows protects you from some other situations in which you shouldn’t convert a basic disk to dynamic by blocking the action. For example, you can’t convert the hard disk in some portable computers to dynamic. Some older portable computers lack the mechanism that Windows uses to detect that the disk is a part of a portable computer. On these computers, a dynamic disk conversion may be possible, but isn’t recommended.

Windows also prevents you from converting disks that have a sector size above 512 bytes or on removable disks such as a Zip drive or a portable hard drive. Finally, Windows won’t let you convert a basic disk to a dynamic disk if the disk is too full. Remember that the disk you’re converting must have room for the dynamic disk database, which consumes the last MB of space on your hard disk. If you created your partition structure with Windows XP, Windows automatically reserves this space so that you can convert to a dynamic disk if you so desire. If you created your partition scheme with another operating system, though, there’s a good chance that the necessary space at the end of the disk doesn’t exist. In that case, if you wanted to convert the basic disk to a dynamic disk, you’d have to back up all of your data, repartition the drive, restore your data, and then do the conversion.

Converting a basic disk into a dynamic disk
Now that I’ve gone over the do’s and don’ts, let’s look at the conversion process. To convert a basic disk to a dynamic disk in Windows XP, open the Disk Management console (at the Run command prompt, type Diskmgmt.msc) and select the disk that you want to convert. Be sure to select the disk and not the partition. Now, right-click on the disk and select the Convert To Dynamic Disk command from the resulting context menu. At this point, you’ll see a dialog box asking you to confirm the conversion. Make sure that the appropriate disk is selected and click OK. If the disk meets all of the criteria that I described above, it will be converted.

With the introduction of Windows XP, we’re beginning to see compelling reasons for conversion to a dynamic disk format. The flexibility and fault tolerance aspects of dynamic disks that are recognized in Windows XP will make them popular with your power users. Because of the potential difficulties associated with dynamic disk conversion, I explained the necessary precautions you should take before performing the conversion.