I did this and it worked.

I downloaded the new 5.xx form the main web site
Lime Wire » Official Website & Free Download, BitTorrent «

but first went into Users\myusername\Appdata\roaming\limewire\version. key
I saved this file version.key and set it aside.

I never uninstalled anything of the versions
Then installed 5.xx
it ran fine.
then close it and then copied the version key back in where I got it from
then install LW 4.12.6 Pro over top of the 5.xx

The Firewall,,World and Wall still shows up.

I don't know why it worked but it did. I tried many other ways till this worked.

It runs fine on my system. Hope it works for your to.

I got LW 4.12.6 to run on Vista 64bit