Fancier align-regexp?

[jrwats]

Input:
Lorem ipsum dolor: sit amet
consectetur: adipiscing elit. Etiam
sed purus: Vestibulum
ante: ipsum
primis in: faucibus

You'll have to paste the following into emacs I'm afraid (or set your
browser to monospace font?) to get this to look 1/2 decent.

I want (the colons aligned with the words preceding them "following"
the colon to the aligned point)
 Internet IP Address:   67.170.74.92
         Subnet Mask:   255.255.252.0
     Default Gateway:   67.170.72.1
                DNS1:   68.87.69.146
                DNS2:   68.87.85.98
                DNS3:   68.87.78.130


calling align-regexp on ":" doesn't work obviously and puts the spaces
between the words preceding the colon:
rem ipsum dolor : sit amet
consectetur       : adipiscing elit. Etiam
sed purus         : Vestibulum
ante              : ipsum
primis in         : faucibus

I know align-regexp has a fancier method to use with a prefix arg, but
I'm not smart enough for it.  Is it possible to accomplish this with
align-regexp?  A macro?