Not all of my RAM is usable

Have you tried reseating the memory and clearing your CMOS?

Clear CMOS - 3 Ways to Clear the CMOS

If this doesn't help go over the settings in BIOS setup with a fine-tooth comb.

And try every slot config.

I would switch to 32 bit if you cannot fix this.

Yep I took a look at it. When I take one out, it still list only 2g usable. When I put 2x512 MB sticks, they both work.

So 32 bit would support 4gigs of RAM?

32 bit would run on a computer with 4 GB of memory, but it doesn't support all of it. 3.25 GB is around the max you'd be using.

On resource monitor it is saying I have 2049 MBs Reserved for Hardware.

Look at the video card settings in BIOS.

Anything in particular I should be looking for?

How much RAM is reserved?