HKey class instances are used to access registry keys.
Available in 3ds Max 2008 and higher. Previously available in the Avguard Extensions .
HKey <HKey parentKey> <string keyName> <int writeAccess>      
Opens existing subkey of parentKey.
This constructor is not typically used, instead the method registry.openKey() is used.
<HKey>.parentKey : HKey - read-only - parent HKey   
Contains the parent HKey of the sub key.
<HKey>.name  : String - read-only - subKey name 
Contains the name of the sub key.
<HKey>.accessRights : Integer - read-only - access rights flags 
Contains the access rights of the sub key (see tables below)
writeAccess values are as follows (see platform SDK help file for more info):
STANDARD_RIGHTS_READ | 
0x00020000 | 
STANDARD_RIGHTS_WRITE | 
0x00020000 | 
STANDARD_RIGHTS_ALL | 
0x001F0000 | 
KEY_QUERY_VALUE | 
0x00000001 | 
KEY_SET_VALUE | 
0x00000002 | 
KEY_CREATE_SUB_KEY | 
0x00000004 | 
KEY_ENUMERATE_SUB_KEYS | 
0x00000008 | 
writeAccess values for common access types are:
#readOnly | 
0x00020019 | 
#writeOnly | 
0x00020006 | 
#all | 
0x000f003f |