Windows process using tons of my physical memory

In task manager I can see the process svchost.exe taking up anywhere from 5-25% of my CPU usage, and much more of my Physical Memory usage (constantly between 70-90%).

I used process explorer to open up the threads for svchost.exe and I can see multiple instances of ntdll.dll!RtlUserThreadStart using up to 10% of my CPU and having very high "Cycles Delta" numbers. Not sure if that is the source of my problems or how I would fix that if it is.

Dell Latitude E6430 Intel Core I5-3320M CPU @ 2.60GHz 4 GB RAM Windows 7 64 bit

Thanks,
Griff