Registry Key extraction and migration

[ed]

Hi I want to write a tool to do the following:
1. extract and display registry keys under abritrary starting point,
for example:
source are: HKey_Local_machine\software\old_lcoation or
HKey_current_user\software\XXX\YYY

a) then, I can specify where the Keys can be copied and compare the
new location to the new location. For example: destination are:
HKEY_local_mahcine\software\New_location.

b) if the keys are not there flags error message

how canI do that?