Loading huge numbers of images

Question

I'm running an iMac quad core i7 with 8GB RAM so plenty of power, but Bridge CS4 seems to take ages to load up the thumbnails of my images.
I have thousands of them all in different folders but all on one external drive. 
I'm going through the painstaking task of tagging/keywording them so I can access them quicker.
I believe the only way I can do this is by loading all the images into one folder, am I correct in this?
Secondly it's taking ages everytime to load up all the images because there's so many, is there anyway to load them all into one folder and kind of capture the contents of this folder, so it doesn't have to start at the beginning loading up all the images from scratch everytime?
Thanks.

Answer 1

Odd thing is happening Curt, I look at Preferences in Bridge and it seems hard to assign a specific GB as the slider is in the range of 10,000 to 500,000.  Anyhow I've set it about 20% of the way down. There's 1TB of storage on the external drive, 1TB on the internal both half full.
Found this when I look at Photoshop Cache,   It seems that when I go into Preferences > Memory Usage its saying the available RAM is 3072MB, with an ideal range 1689-2211MB/ Let Photoshop use 70%.
There's 8GB RAM on the system, any reason it's only recognising 3GB of it? Could this be a reason for poor performance or is Photoshop nothing to do with Bridge in loading images in Bridge?
Bridge
Photoshop