Hi Wendylau,
Were you able to see the disk defragmenter on the comptuer earlier?
Step 1
I would suggest you to check for the defrag.exe or defrag file in the following location and check if you can run the disk defragmenter from that location.
- Click on Start.
- Click on Computer.
- Navigate to the followinf location.
- C drive > Windows > System 32.
- Check for defrag.exe or defrag file.
- If you find the file try to run it from there and check if you can run disk defragmenter.
If you want the file to be put into Start menu, you may right click on defrag or defrag.exe and click on pin to start menu and check if it appears in the start menu.
Access the link below to know how to run Disk defragmenter on the computer.
http://support.microsoft.com/kb/314848
Step 2
If the above steps do not help, you may try to runSystem File Checker (SFC scan). The System File Checker tool to determine whether the issue that you are experiencing is caused by one or more system files that are used by Windows Vista, The System File Checker tool scans system files and replaces incorrect versions of the system files by using the correct versions.
To run the System File Checker tool, follow these steps:
a. Click Start, and then type cmd in the Start Search box.
b. Right-click cmd in the Programs list, and then click Run as administrator.
If you are prompted for an administrator password or confirmation, type your password or click Continue
c. At the command prompt, the following line, and then press ENTER: sfc /scannow
When the scan is complete, verify if you can find the disk defragmenter is back on the computer. Access the link below to know more information about System File Checker tool
http://support.microsoft.com/kb/936212
Hope this helps. Let us know the results.
Thanks and Regards,
Srinivas R
Microsoft Support.
Visit our Microsoft Answers Feedback Forum and let us know what you think.