For Those people who like to tweak you network card speed Manually.
Step 1
Open Contorl Panel -> Open Network Connections
or
Just right click on your network connection on Desktop bottom right
Step 2
Look for you LAN connection or your network card and right click
Select Properties and you will see 3 tab = General , authentication and advanced
Under General Tab you will see the network can name and a button on the right " Configure"
Step 3
Click on "Configure" and you will see 5 tab = General, Advanced , Driver , Resources , Power Management.
Click on "Advanced" tab and you will see 4 selectable line in the box.
Please select "Speed and Duplex" and you will see on the right there is a box which has value and inside the box is Auto.
Step 4
Click on the Auto area a list of Speed supported will be come up and select the speed you want.
End
This Guide help you check your speed in case you wonder which your network is only connecting at 10 instead of 100 but it might be from your modem/router also
Cheers