Windows defender won't turn on

I recently noticed that windows defender had been off and I turned it on and scheduled daily scans and reset a few options.
Then yesterday, I find that windows defender won't turn on at all.
I know someone hacked my system. Apparently in my home at some point and attached a device via bluetooth and then hid all acess to blue tooth controls.
I know nothing about programming. But when my computer started acting odd, I tried to trouble shoot as best I could.
Last month I had to do a system restore.
Latest problem is windows defender is no longer accesible in any way that I can find and I've tried a few ways. It just won't open.
Ideas?

 

Welcome to Major Geeks!

What is your Windows version?

What I would suggest at this time is to uninstall Windows Defender, and install Microsoft Security Essentials instead: http://www.microsoft.com/en-us/download/details.aspx?id=5201

 

Download and run the following program from major Geeks.

Malwarebytes Anti-Malware

 

Hi my friend , Welcome to MG's :major

Also you can run this on line antivirus :wave

http://www.eset.com/home/products/online-scanner/

 

Eset has no mention of Win 8.

 

peterr, Windows Defender was included in Vista and 7 so until the OP tells us, we can't guess if he/she is running XP, Vista, 7 or 8. :confused

 

I thought I had MSE with Win 7 and now have Defender with Win 8 but I could be mistaken about 7 -it has been awhile.
Yes, it would help to know the os.

 

You can download MSE for 7 but it comes with Defender, trying to protect computer users until they install something.
The Window Defender of 8 IS NOT the Windows Defender installed on 7 and Vista. MS continues to recycle words to confuse users. Defender of 8 is actually like MSE.

 

Well, they certainly succeeded confusing me especially, "Defender of 8 is actually like MSE." What's next, maybe an old build with a new name.
Thanks