User Key: [HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\
Advanced]
System Key: [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\
Advanced]
Value Name: TaskbarGroupSize
Data Type: REG_DWORD (DWORD Value)
Value Data: Number of windows (default = 3)
Posted by PaulElso