disk defragmenter cannot start becuase the task scheduler service

Could be malware/virus?

Thanks for the comments. Re-format and re-installed Win7 and it worked properly. Should have done it in the first instance. Suspect it may have been from the third party driver providers when I was looking for my broadcom wireless card driver; even though I did not download their drivers but just stopped when they wanted to charge to download their driver. Later found out that the wireless driver was in the windows update.
Lesson learnt is after installing the Win7 OS to download all the Windows updates and install them before installing other programs.

One thing that could keep you from doing defragment is your Administrator account doesn't have all privileges/permissions that you think it must have. Or even Administrators group hasn't been added to security list of the executable file you are trying to open (defrag.exe).

The following will help:
Open Computer -> right click on disk C: -> click properties ->hit security tab ->hit edit-> hit add-> hit advanced-> hit find now -> find your login name in the list you might add Administrator and Administrators as well -> hit ok-> hit ok-> find your name in the security list click on it and check allow on all permissions.

I deleted the "Defrag" folder in Task Scheduler because I only want to run Disk Defragment manually. However, Disk Defragment can only run if there is a "Defrag" folder in Task Scheduler. If you need to put it back, run Task Scheduler, go to Task Scheduler Library, Microsoft, Windows. If there is no "Defrag" folder, click New Folder, and add a "Defrag" folder. Then reboot and try to run Disk Defragment.

To solve this
go to services
win+r and type services.msc
go to task scheduler and see if its stopped
than go to windows event log service and change its start up type to automatic, than click on start service
now go back to task scheduler service and change its start up type to automatic, than click on start service
and it will be solved

Same issue here can't use defrag, can't start task sched