HTC Aria :: How Do I Access The Phone Memory (not SD)?

My phone is notifying me that it is low on memory, which I assume to mean a portion of the memory that is independent from the SD card, because that has 1.75GB free. I would like to remove some of this data (it's probably because of my 500 pictures), but the only place I can think of to delete the pictures won't let me access them BECAUSE I have low memory. I've searched through the settings application, but can't find anything for manual handling of data.I'm pretty comfortable with technology, but this is ridiculous. Even my old Samsung picture phone had data managing tools. I hope I'm just not looking in the right place.I've got it plugged in to my PC via USB right now, but the folders aren't named very conveniently. I have no idea what is phone memory?

So I think by mounting the phone via USB, I am ONLY accessing the phone memory. In that case, I need to access the SD card, so I can move some of this stuff over. I'm very confused though, because when I open the drive in My Computer it shows it as being a nearly empty 1.84 GB drive, which the phone memory should not (as far as I know) have, especially if it's full. This leads me to believe that it is in fact the SD card, but AGH.