press Start–>Run and enter the the following command in the open line
reg export "tree" file name
where the “tree” is the registry tree you need to export (tree should be embraced with quotes);
file name is the file where the result will be saved.
For example, you need to export the
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control tree into the C:\result.reg file
The command will be as follows
reg export "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control" c:\result.reg