It used to be that when I downloaded a brush, I put it into the Preset, Brushes folder and when I clicked on the little arrow to get the list of brushes (sorry I don't know what everything is called), I didn't have to click Load or whatever... it was on the list along with the ones that came with the software. I don't know what or when something changed, but now the name of the brush is not automatically on the list... I have to load it. And when I load it, it's appended to the end of the regular set of brushes. Before, it would open just the set that I clicked on and I would not see the regular ones... It would replace the current set.
It was very convenient to have them on the list without having to Load them each time. Is there some way I can get back to that?
After putting a brush-set file in the presets folder and relaunching Ps, the brush-set should be a new item in the menu you mentioned, but the actual brushes within the brush-set still have to be loaded. That seems to be happening correctly for you.
When you load the brushes from a brush-set, you have the choice to either completely replace your currently loaded brushes or to append the new brushes to the currently loaded brushes. Seems like you made the wrong choice.
It is Windows 7 64 bit and 64 bit Photoshop.
When I put the brush into the folder (shown above) and restart PS, the name of the brush does not appear on the list in Photoshop. If I load the brush, the actual brushes append to the regular brush selection (not the list where you would change to a different set, but the actual brushes).
That's because it's the wrong folder for 64 bit Photoshop. Try this one instead:
C:\Program Files\Adobe\Adobe Photoshop CS5.1 (64 Bit)\Presets\Brushes
Be advised that the C:\Program Files (x86) folder subtree is for 32 bit software.
Generally speaking, I'd advise against writing anything into the Photoshop installation area. As I recall Adobe has provided you a user-specific place into which to put your brushes, which would both allow you to add to the preset default list, as well as keep the installed file set under Program Files clean.
See if this will work instead:
C:\Users\YourUsername\AppData\Roaming\Adobe\Adobe Photoshop CS5.1\Presets\Brushes