I'd try another computer, or perhaps get online using some Linux Live CD or something. That way you could eliminate the possibility of it being a software problem. The different speeds among your machines make me think you may have some sort of software hindering the speed, at least on the desktop. Perhaps an over-protective firewall or spyware?
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Desktop * Athlon X2 4200 | 2G RAM | 160G HD | 7600GT
Laptop1 * C2D T5550 | 3G RAM | 120G HD | Intel x3100
Laptop2 * C2D T5250 | 2G RAM | 160G HD | Intel x3100
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