Check if it is a 10/100 NIC...Maybe it is set to autodetect and is only RUNNINg at 10Mbps
To fix this in any MS OS I will give you the universal way to access the NIC
Go to the Device Manager which for 98 is R-click on MY computer and Click the Tab
For Win2k or Xp is Right Click My Computer and then click hte Hardware Tab, and then click Device Manager
THEN....
Click the option for Network Adpater and expand the menu and right click on yours
The go through the tabs until you see one that has TWO columns...
Find the Network Media choice on the left, and the corressponding choice On the Right should be set to auto sense.
Set it to "100MBps" if your Hub/switch allows fot it
Good Luck