memory, I had your exact setup (Pentium D 820 and a Pentium 3) for quite some time, so I should be able to help you there.
Are you folding 24/7 on the Pentium D 820? If so, download the Windows SMP Client.
Instructions are here:
http://www.computerforum.com/754116-post1686.html
If you run your Pentium D 820 24/7 with the SMP client, you should be getting around 600 to 750 Points Per Day (PPD). Each Work Unit (WU) is usually worth 1760 points, and takes around 2-3 days to complete.
If you run your Pentium D 820 24/7 with two normal clients, expect around 400PPD total.
As far as your Pentium 3 is concerned; Pentium 3s are actually quite good folders. With my 1Ghz, I get/got around 80 to 100PPD. If you need any help, don't hesitate to contact me!
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On another note, I just installed an E4500 in my desktop. At stock speeds (which it won't be at very long, no doubt), it just did a 19 minute frame, or in other words around 1200+ PPD. Keep folding!