Click on Start -> Run -> and enter the following regedit command in the run dialog box,
regedit /e "%userprofile%\desktop\putty-sessions.reg" HKEY_CURRENT_USER\Software\Simontatham
regedit /e "%userprofile%\desktop\putty-sessions.reg" HKEY_CURRENT_USER\Software\Simontatham
File will be created in the desktop of your
system. copy the file in the target system and double click on the registry file and accept to add to your registry.You will find all the session in your putty.