Just to explain for future readers, on x64 systems there are two system folders. C:\Windows\System32 is where 64-bit components are stored, and C:\Windows\SysWOW64\ is where 32-bit components are stored. 32-bit Applications, however, will get magically redirected to C:\Windows\SysWow64 if they access C:\Windows\System32. This causes a lot of confusion.
There is also redirection in the registry, which is probably relevant here.
regsvr32.exe in C:\Windows\System32 would be the 64-bit program, which registers and unregisters 64-bit components. It acts weird with 32-bit components, and when it does work, it registers it into the main registry.
the regsvr32.exe in the SysWOW64 is the 32-bit version, and will register 32-bit components in a way so that 32-bit applications can see them; (registry access by 32-bit applications in HKEY_CLASSES_ROOT get's redirected to "HKEY_CLASSES_ROOT\WOW6432Node" instead, so 32-bit applications will be looking for the component registration there.