not enough : there's a key in HKCU\SOFTWARE\7-zip\Plugins for each extension/plugin. (witout these, 7-zip doesn't know it's associated : can be useful, can be useless, i let you find what it changes...)
edit: in HKCU, not HKLM :
CODE
Windows Registry Editor Version 5.00
[HKEY_CURRENT_USER\Software\7-Zip\FM\Associations]
[HKEY_CURRENT_USER\Software\7-Zip\FM\Associations\001]
"Plugins"=""
[HKEY_CURRENT_USER\Software\7-Zip\FM\Associations\7z]
"Plugins"=""
[HKEY_CURRENT_USER\Software\7-Zip\FM\Associations\arj]
"Plugins"=""
[HKEY_CURRENT_USER\Software\7-Zip\FM\Associations\bz2]
"Plugins"=""
[HKEY_CURRENT_USER\Software\7-Zip\FM\Associations\cab]
"Plugins"=""
[HKEY_CURRENT_USER\Software\7-Zip\FM\Associations\cpio]
"Plugins"=""
[HKEY_CURRENT_USER\Software\7-Zip\FM\Associations\deb]
"Plugins"=""
[HKEY_CURRENT_USER\Software\7-Zip\FM\Associations\gz]
"Plugins"=""
[HKEY_CURRENT_USER\Software\7-Zip\FM\Associations\lzh]
"Plugins"=""
[HKEY_CURRENT_USER\Software\7-Zip\FM\Associations\rar]
"Plugins"=""
[HKEY_CURRENT_USER\Software\7-Zip\FM\Associations\rpm]
"Plugins"=""
[HKEY_CURRENT_USER\Software\7-Zip\FM\Associations\tar]
"Plugins"=""
[HKEY_CURRENT_USER\Software\7-Zip\FM\Associations\z]
"Plugins"=""
[HKEY_CURRENT_USER\Software\7-Zip\FM\Associations\zip]
"Plugins"=""
each of these keys matches one checkbox in the 7zip options