Windows users experiencing slow uploads on a fast internet connection may need to adjust TCP frames that are limited out of the box by the operating system.
Click Start > Run and type REGEDIT and click Enter.
Then find the registry entry below.
Create a new DWORD 32-bit string in Parameters and name it "DefaultSendWindow"
Double-click the DefaultSendWindow entry and choose Decimal and type the value 1640960
Restart the machine to apply the changes