It is generally best practice to either fully path the DLL to be registered, or register once inside the folder that contains the DLL.
Use your CMD session to move between folders.
Finally, some work best if using the "/i" option, although I have no idea why.
Syntax
regsvr32 [/u] [/s] [/n] [/i[:cmdline]] dllname
Parameters
/u
Unregisters server.
/s
Specifies regsvr32 to run silently and to not display any message boxes.
/n
Specifies not to call DllRegisterServer. You must use this option with /i.
/i:cmdline
Calls DllInstall passing it an optional [cmdline]. When used with /u, it calls dll uninstall.
dllname
Specifies the name of the dll file that will be registered.
/?
Displays help at the command prompt.