Most likely it's not the motherboard or the bios. At this time I recommend leaving the bios as they are.
I'm not quite sure what you mean by slow. Slow when and doing what?
According to the pictures in post #9 Windows is using your ram correctly.

This tutorial might help speed things up a bit. Their are some good tips that might help. Some I don't agree with and some I do. It's a good read.
Place close attention to #8. I don't recommend messing with Microsoft Services.
Checking NON Microsoft Service is a good thing to do.

By Brink:
Optimize Windows 7

Keep in mind that this all happened when you removed ram.
I also like to make sure the computer is free of infection and other little bad things.

***What security programs do you have install??
Please List all of them.

Could you post a picture of msconfic Startup and Non Microsoft Services.