FFXI and VistaFollow

I hope I'm not repeating a post, but I did not see this issue on the Forum. I apologise if I am.

I used to play FFXI on the 360 and have recently returned and started over on my PC. One of the issues I've found is when I enable Windowed Mode in POL config, it does not reflect ingame. Any attempt to alt+tab out of FFXI results in an error and full screen mode is terminated. The solution, I've been told, is to download the Vista version of POL directly from the official FFXI website. My question is will I have to redownload FFXI? Or do I need to uninstall my current version of POL? Would it simply update my version of POL?

Any help is appreciated! Thank you very much. ^^