As described by this Microsoft TechNet article you can load a
.dat file into an existing registry:
To load a hive into the registry
- Open Registry Editor.
- In the registry tree (on the left), click either the HKEY_USERS or HKEY_LOCAL_MACHINE keys.
- On the File menu, click Load Hive.
- In Look in, click the drive, folder, or network computer and folder that contains the hive you want to load.
- Click Open.
- In Key Name, type the name that you want to assign to the hive, and then click OK.
You can then browse the tree and export the PuTTY configuration from
HKCU or HKLM\Entered Key Name\Software\SimonTatham\PuTTY
For the bit where you want to add the old registry settings into your new registry. Before using 'File > Import' to import your .reg file, do the following (I did this on my Windows XP machine and it worked)
- Open your saved .reg file in an editor
Replace all occurences of 'HKCU or HKLM\Entered Key Name' with 'HKEY_CURRENT_USER' so that the reg paths look like the following:
Windows Registry Editor Version 5.00