Yes, some may consider a computer from 2009 ancient ... but I use Lr with a late 2007 Macbook Pro and don't seem to suffer from undue harm.
Where your RAW images reside, and how they are accessed by Lightroom can be a factor. If your external drive is USB2 ... and your RAW images in the 16MP or greater range, you can indeed expect Lr not to be instantly responsive.
You really need to share more information as to the details in your hardware configuration, the size of the RAWcamera files you use most often and the exact configuration of your external drive so we can better assess your question.
Thanks Butch, I do have large sized images - in the 28 MP range. And my laptop was 4GB with 256 memory.
To avoid clogging up my hard drive, I was keeping the photos - about 4,000 of them on a separate portable drive, a 1TB MyPassport for Mac drive with - indeed, a USB2. So it sounds like the size of my images and this slow transfer is probably a big part of my problem.
I have just upgraded my macbook pro to a new 15" 8GB with a 256 SSD. And I would like to set up properly. I still would prefer not to have all the photos reside on my hard drive. I also have an iMac with a much larger drive, so I guess I could keep the catalog and the photos on it instead - but I don't like to work in my basement space where the desktop is....thus why I've been using laptop.
Any suggestions would be most welcomed. I also have a rather large inventory of previous photos that are in jpg format to be moved from iPhoto. But that is a question for another day. My immediate challenge is to figure out a workflow that is not too slow but does not eat up my hard drive. Danielle