In previous versions of the Disk Defragmenter that came with Windows, you had the option to analyze drives only without performing a full defragmentation. This way you could see if a particular drive really needed this task performed or if you could wait a while.

Unfortunately, the Windows Vista Disk Defragmenter GUI lacks this option. However, the command-line tool does support analyzing a drive.

First run the Command Prompt as an administrator:

1. Click the "Start" button and type cmd.

2. When "cmd.exe" appears, right-click the icon and choose "Run As Administrator".

3. Confirm your actions if User Account Control (UAC) prompts you.

Now, for the command:

4. Enter the defrag command at the prompt, passing in the -a command line option and the name of the volume to analyze.

For example, to analyze drive M:, enter the following command:

defrag -a m:

Output will appear similar to the following, showing basic fragmentation information and a suggestion on whether or not you need to manually defrag the drive:

Windows Disk Defragmenter
Copyright (c) 2006 Microsoft Corp.

Analysis report for volume M:

Volume size = 10.00 GB
Free space = 9.84 GB
Largest free space extent = 5.00 GB
Percent file fragmentation = 0 %

Note: On NTFS volumes, file fragments larger than 64MB are not included in the fragmentation statistics

You do not need to defragment this volume.

You can optionally add the -v command line parameter to display more information such as specifics on file, free space, folder, and Master File Table (MFT) fragmentation.

For example, the following command analyzes drive C: and displays verbose information in the analysis:

defrag -a -v c:

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