I bought Street Fighter IV and when you start the game it asks for you to create or use an existing profile.

Any Game for Windows Live will enable you to create a profile that have all your games and you can show to other people what you have been playing. For example, see Microsoft Xbox Live Director of Programming Larry Hryb gamertag Major Nelson.

You enter your an email address and the password and it will download your profile to your computer but in my case it said “Can’t connect to Live – Error 0x80151911”

I read that the culprit was the MTU parameter set on your network. It can be set in any part of your network like your router or your Windows computer.

You need to set the MTU size to at least 1400 to make it download the profile. See your router documentation on how to change this parameter.

On a Windows computer you need to open regedit.exe and then search for the entries called MTU in HKEY_LOCAL_MACHINE/SYSTEM/CurrentControlSet/Services/Tcpip/Interfaces and select each interface (a random string of numbers). Right click the parameter MTU and choose decimal then type 1492 or 1500. Now you should be able to download your profile.