Please help: Slow speeds

I have a really bizare problem that I am hoping someone can help with.
I have a Netgear DG834v2 router (although I think the router its self is
irrelevant to the problem), it is connected to a BT 512k DSL connection. On
my machine I only get 300kb/s down and 150kb/s up. This is however only on
my machine, any of the other computers in the house are fine and get 464k
down and 235k up. So I'm guessing it's a network setting problem on my
machine. All computers are running Windows XP SP2, and connected via either
a built in 100mb/s LAN, or Belkin 11mb/s wireless cards. I've tried the
router connected to 2 of the machines via both methods, and mine is still
slow, while the other gets the right speed.
I tried running a program called DSL Speed (v2.02), to correct Windows
settings as I do not know a great deal about network settings. It doesn't
seem to make any difference weather it's run or not, or if its installed or
not.

Please help as this is getting seriously annoying!

Pete.