To Ohjiro Watanabe, Mike Denneny
Thank you very much for your suggestions.
Drive C is indeed a SSD, and less than half full. I keep my SL application there.
I excluded all the SL files from the Norton virus checker. I also cleared my cache, both inventory and regular. That didn't help on the fps.
Here's what I did do. I rented an Alienware laptop gaming computer, installed Firestorm on it, and logged in. It got 40 to 50 fps. The network communication speed was the same as for my desktop, and I used a cable. The Alienware computer had an i5-4200 M CPU, 2.50 Ghz, 8 Gig ram, Windows 7 64 bit.
Graphics was a Nvidia Geforce gt 750M. The screen resolution was 1366 x 768
I set my computer to the same resolution and did all the things you advised. It still got between 15 and 20 fps, at the lowest graphics setting, no shaders, and the lowest distance drawing.
I can only conclude that the motherboard, and/or the CPU made the difference. I doubt if the gt 750M would match the MSI GTX 970 that I put in my computer. My motherboard had the AMD Phenom II X4 955 Processor (3210.77 MHz). It also had the PCI Express 2.0, while the gtx 970 uses a PCI express 3.0, but is backwards compatible.
I tried to eliminate any issues of firewall compatibility or network speed by attaching both the computers to the same router by cable. I turned off the Norton firewall completely for several tests on my computer, and it made no difference. Also, I turned the hardware router firewall to its lowest protection for both computers.
I don't mind getting a new computer, but I wanted to eliminate all the possibilities. It was jarring to me that replacing the GTX 580 with the GTX 970 made no difference whatsoever, but I guess the bottleneck was really the old AMD CPU, and the old motherboard.
I would be happy to hear any other ideas. I tried to insert a snapshot of the graphics settings, but I'm not sure how to paste an image here.