Navigate the the location below in your registry and make the corresponding change.

Create or edit the existing two DWORD values named 'MaxConnectionsPerServer' and 'MaxConnectionsPer1_0Server'. 

Change the values to equal the number of simultaneous requests allowed to a single HTTP server, the default values are 2 and 4.

Restart Windows. 


Key:[HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings]
Data Type: REG_DWORD
Data:Number of Simultaneous Connections
More info: http://support.microsoft.com/support/kb/articles/Q183/1/10.ASP