odd processes

So, in my continuing effort to suss out my ailing computer, I'm wondering if anyone can identify/advise me about the following processes running (and chewing up) a lot of processing power of my CPU that I find in my Windows Task Manager:

MsMpEng.exe
MRT.exe
MSASCui.exe

what do these do? what are they running? if they're crap, how do I get rid of them? what came first, the chicken or the egg?

Help!

thanks,
s1mpl1fy

 

These are related to Windows Defender, here is a read on MSAC,

http://www.justtext.com/processes-tasks/msascui-exe.html

 

Wow!

What an awesome reference tool...

Thanks so much...I'm now going to spend the next hour plowing through every process to make sure they're all legit.

Thanks so much!

s1mpl1fy