OK Windows have some limitations (who knows why) of the bandwidth. Here is a little guid on something that might help you:
1-Open Run dialog box from Start menu.
2- Type “gpedit.msc†and press Ok.
3- When Group Policy run, go to Local Computer Policy > Computer Configuration > Administrative Templates > Network > Qos Packet Schedule
4- in right side, right click on Limit reseivable bandwidth and select Properties.
5- In Setting tab under Limit reservable bandwidth section select Enabeled .
6- instead of 20 type 0 (zero) and then click ok, and close Group Policy.
7- Now , go to Network connection and right click on your connection and select Properties.
8- Go to Networking tab and cheek Qos Packet Scheduler to be ticked.
9- Restart your PC
if you think this makes your server slower than before just switch to the default values and everything will run as it had. I see some improvement for me.
Hope I helped