Windows Defender missing/not working.

[Zalkard]

So, I had to reinstall windows cause my hard drive died.
Since I only have a windows 8 CD, I have to install windows 8, and then update to 8.1.
Now I'm finished installing and putting programs back on, I notice my windows defender isn't working/isn't there. Is there any way I can get windows defender from somewhere without reinstalling windows?

 

[TheDualshock]

You should go with a different anti-virus. I've got AVG for free and it seems to work fine, no bugs or anything with my PC.