The reason why Disk Defragmenter is not functioning is because page file is turned off. How to turn the page file on, you need to do this: Click on Start - My computer, right click it and click on properties
In the Properties window that opens up, click on the Advanced Tab and in Performance Area click on the Settings button.
In the Performance Option window that opens up, under the Advanced tab, in the Virtual Memory Area, click on the Change button.
In the Virtual Memory window that opens there is an option, System Managed Size, select that and press on the Set button, followed by clicking on OK.
After which you need to restart the PC, right away, else all the settings that we made will be futile. The next time, after rebooting, the disk defragmenter will work fine.