Are you testing across your LAN only or out to the internet? What tool are you using to test your connection?
i am having a very strange problem i have exhausted all options that i can think of. Ok here's the problem My main pc is connected to a router the router is a linksys WAG354G, i did a speed test and the pc always gets a speed below 512mb but i am on tiscali 2mb so it should be around 1.44mps or higher, here's the pc spec's cpu:amd xp3200 2.2ghz ram:1gb motherboard:asrock k7vt6 power supply 400watt generic came with case, And i have used 2 diffrent network adapters same problem one adapter was the on-board the other a netgear fa311. So i tried my laptop which is a acer spec's sempron 2800+ 256mb ram, so i connected it into the router using the same cable that my pc used, did the speed test and it turned out that the laptop was getting 1.44mps, so I went back to my desktop pc disconnected the router and powered it down, i then reconnected the usb modem that was provided with my net package did a speed test and it got 1.74mps.
heres what I have done to the desktop to try and fix the problem
re-formated the computer with windows xp home edition with service pack 2
reseted the cmos
tried 3 different network cables
tried alot of tweak sites
but still no luck. I was wondering if you could help, It only started happening like 3-4 weeks ago and i have put everything back to default ie reformatted and the bios has been rested using cmos jumpers.