Defrag

I am trying to defrag the hard drive but when I tried to analyze/defrag it says chkdsk is scheduled to run. How do I correct this?
Thanks

Try restarting your computer. After you restart, see if a blue disk check screen appears. Allow it to run. It will then restart itself. Try it then.

go into task manager processes tab and end them all but explorer, system and system idle process then try defrag it always works for me. you will have to restart after defrag.

hope this helps if you have not sorted it yet