Oh yes, and you said it is fine, right? What kind of speeds are you getting on it?
Yeah, changing hardware is not going to matter if the problem is software, which I'm thinking it must be.
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Have you tried setting the duplex of your network card to 100Mbps/Full-duplex? Your router may not support it (most do), but some ppl see speed increase when the duplex is forced instead of auto-detect, because it relies less on resources.