My cousing had been troubleshooting this for a few days and after starting to get involved in the troubleshooting the same problem occured on my main computer as well. There was no chance to increase the download above 1.3MBs (got 200/200 connection), unless downloading from a service that uses swarm tech (i.e Steam, Origin etc).
After backtracking we came back to Hamachi and this thread. We finally found the solution that worked for us. It seems installing Hamachin changes the TCP Global Parameters. To check/fix this, do the following:
SOLUTION:
Start -> Run -> CMD (as administrator to buypass the UAC)
then type the following command to show what parameters your current TCP has:
netsh interface tcp show global
This should give you a list over the TCP parameters, the ones Hamachi seems to change are these two:
Receive-Side Scaling State& Receive Window Auto-Tuning Level. Recieve-Side Scaling State was set to 'disabled' and Recieve Window Auto-Tuning Level was set to 'disabled'
Type the following commands in the CMD to change this:
netsh int tcp set global autotuninglevel=normal (Response should be OK.)
netsh int tcp set global rss=enabled (Response should be OK.)
Reboot shouldn't be needed after, but if you encounter problems do it. We didn't test Hamachi after this because we uninstalled it so I don't know how it works after this change.
I have no idea why Hamachi changes these parameters on some/all computers? When we checked other hosts in our network running the same OS without hamachi these parameters where unchanged and download speed OK.