Thank you to all who shared their knowledge. I am updating this thread in case it helps anyone in the future.
Two days ago I removed the two factory 512MB cards and replaced them with two Kingston 1GB cards. That was a great move. My computer is faster and pages all behave themselves now. It is like getting a new machine.
Any thoughts on whether the factory cards were corrupted or just undersized? Shoud I install them in the #3 and #4 DIMM spots or leave them out?
Some praise for Kingston. I originally went to their site to see if I could find out exactly what I needed to order. I did not know they also had an online store. The search function was great if you use the right one. Don't use the generic blank search bar. Use the "search by brand" function. After inserting the brand of computer, a drop down menu allows you to select what model you have. After that a page is displayed with all the Kingston products for that model.
My memory was on "promo" so it was $16/1GB card. Free shipping over $25. They do collect tax for many states. Only complaint is their tracking is slow.

I ordered before noon on Friday and received my shipment in the mail on Tuesday (Monday was a holiday). Tracking still showed it as "order received". Their shipping is so fast their tracking programs can't keep up. Great job Kingston.
