Czy możliwa jest modyfikacja wpisu do rejestru poprzez.bat/.skrypt cmd?

Możesz użyć polecenia REG. Od http://www.ss64.com/nt/reg.html :

Syntax:

   REG QUERY [ROOT\]RegKey /v ValueName [/s]
   REG QUERY [ROOT\]RegKey /ve  --This returns the (default) value

   REG ADD [ROOT\]RegKey /v ValueName [/t DataType] [/S Separator] [/d Data] [/f]
   REG ADD [ROOT\]RegKey /ve [/d Data] [/f]  -- Set the (default) value

   REG DELETE [ROOT\]RegKey /v ValueName [/f]
   REG DELETE [ROOT\]RegKey /ve [/f]  -- Remove the (default) value
   REG DELETE [ROOT\]RegKey /va [/f]  -- Delete all values under this key

   REG COPY  [\\SourceMachine\][ROOT\]RegKey [\\DestMachine\][ROOT\]RegKey

   REG EXPORT [ROOT\]RegKey FileName.reg
   REG IMPORT FileName.reg
   REG SAVE [ROOT\]RegKey FileName.hiv
   REG RESTORE \\MachineName\[ROOT]\KeyName FileName.hiv

   REG LOAD FileName KeyName
   REG UNLOAD KeyName

   REG COMPARE [ROOT\]RegKey [ROOT\]RegKey [/v ValueName] [Output] [/s]
   REG COMPARE [ROOT\]RegKey [ROOT\]RegKey [/ve] [Output] [/s]

Key:
   ROOT :
         HKLM = HKey_Local_machine (default)
         HKCU = HKey_current_user
         HKU  = HKey_users
         HKCR = HKey_classes_root

   ValueName : The value, under the selected RegKey, to edit.
               (default is all keys and values)

   /d Data   : The actual data to store as a "String", integer etc

   /f        : Force an update without prompting "Value exists, overwrite Y/N"

   \\Machine : Name of remote machine - omitting defaults to current machine.
                Only HKLM and HKU are available on remote machines.

   FileName  : The filename to save or restore a registry hive.

   KeyName   : A key name to load a hive file into. (Creating a new key)

   /S        : Query all subkeys and values.

   /S Separator : Character to use as the separator in REG_MULTI_SZ values
                  the default is "\0" 

   /t DataType  : REG_SZ (default) | REG_DWORD | REG_EXPAND_SZ | REG_MULTI_SZ

   Output    : /od (only differences) /os (only matches) /oa (all) /on (no output)