Is it just the net that is slow? Or is your whole computer slow? If it is the whole thing, it might be that the IDE controller is stuck in PIO mode. You don't mention what OS you are running - if it is XP or Vista they are both notorious for reverting to PIO mode after a while.

To check:

Right Click "My Computer"
Select "Properties"
Select "Device Manager"
Open up "IDE ATA ATAPI Controllers"
Open up each "IDE channel" and go to the "Advanced" tab. Make sure all channels are set to "DMA" and not "PIO".

If you had to change anyone to DMA from PIO, you will need to reboot for it to take effect.

DocZ