aeromed202,
I used to think that once a PC had migrated from Windows Update to Micro$oft Update, that was it. However, I recently found out that you can move "back" to Windows Update if you click on the "change your settings" link on the Micro$oft Update home page, then clear / deselect the option at the bottom of that screen. I've tested it and it does work.
As I said in an earlier post, M$ appear to have changed their policy on version compatibility with v4, though it seems that many people cannot grasp the difference from their old policy or the way that .NET Framework was different from most other software.
Anyway, if you now have Updates working, I think your remaining concern is just how backward-compatible v4 is when used with other products like FSINN. On that, I'm afraid only time will tell, since most people are unlikely to bother testing such things with only v4 installed (by neglecting to uninstall whichever previous version was required). You could of course do as claudius24 suggested and install all the different versions, but then nobody will ever know whether v4 alone meets all your needs,
hope that helps,
Ro