How to: Concurrent connections limit enable/disable in vista sp2
In Vista SP2 it appears the 10 half open concurrent connections limit has been removed but if you want to enable it you can do as listed below in the registry :
type regedit in the Start Search box, and then click regedit.exe in the Programs list.
If you are prompted for an administrator password or for confirmation, type your password, or click Continue.
Locate and then double-click the following registry key:
If it does not exist make a new DWORD
In the Value data box, type 1, and then click OK.
NOTE: 2008 SP2 has a similar key for its use.
And thats it turned on again. If you set it to 0 its off which I believe is the default anyway.
MS Article: http://support.microsoft.com/kb/969710