Here is the breakdown for the MSN Toolbar:
If you extract the setup executable, (you can use winrar or winzip for this), you will find a file called mtbs.exe
Now if you try to pass the normal switches to that program, it gives you an error.
But what I did is try passing the switches that the Messenger 6.2 MSI uses, and sure enough, it accepts them.
So...I tried some others. Here are the ones I found so far that do anything:
(The format is <path>mtbs.exe <switch> There is no "/")
c=Uninstall but not silent
d=Launches the normal install for just the portion that sets the "Making MSN Search your default search engine..." with a check box to change language to english. Along with "Finish", "Cancel", and "Help" buttons.
e=Launches the normal install along with all dialogs, but no check boxes for make MSN default search, or set home page to MSN. (Does not set them)
f=Same as "e" from what I can tell, except it actually sets the Making MSN Search your default search engine..." even though there is no checkbox for it.
i= Launches the normal install along with all dialogs and includes check boxes to make MSN default search, and Set home page to MSN.
j=Silent Install, but also launches IE to the "Get Started" page. (Don't know yet if it sets MSN to be the default search, or not.)
t=Silent Uninstall
u=Uninstall but not silent
So for example, the install would be:
mtbs.exe j
Or what ever switch you want.