Here is an export of (what should be) the relevant registry setting:

[HKEY_CURRENT_USER\Software\Microsoft\Office\10.0\C ommon\HelpViewer]
"DxExpanded"=dword:000000f3
"ExpandedState"=dword:00000001
"FloatingSize"=dword:021302c0
"FloatingPosition"=dword:01340035
"DockedSize"=dword:00000277
"DockedState"=dword:00000002
"IsFloating"=dword:00000001

But bot my Excel and my VBA editor windows still resize when I open the
help.

Can anyone please tell me what I've done wrong?