If I uninstall the sim is there anything that I need to know about that I might not be aware of that I should manually delete? I thought I knew what I was doing but after all this I'm not so sure of that now. lol
Back on 11/07/08 I posted a paraphrase of bulletin from MS on how to do this, it's in the SOH Acceleration Forum.
A thought on the addons installed, you may want to use Add/Remove to uninstall them all first and hope that the registry is okay, (as I understand it, just because you uninstall a program doesn't mean the registry entries are correctly deleted (or changed back to what they were if changed by an addon installation) as well, and that can cause a heap of problems), and any associated backup folders are replaced and there's no left over files hanging around. I've been told it's best to always use the programs uninstaller applet (if it has one) or Add/Remove in Control Panel, don't just delete folders - there's more of them than you can imagine and there in lots of places other than C:\Programs, or whatever. Then hunt down and delete any remaining folders and hope the registry is back to what it should be. The last thing you'll do is actually uninstall FSX.
Personally, as I use the one PC only for FSX, I find it's easier to reformat and reinstall Windows when I get to that point, update the OS and drivers and start fresh, that way I'm not chasing down left over mistakes I previously made on top of the new mistakes I know I'm going to make. But that's just me.
If I were you I'd read some of the other posts here at SOH about reinstalling and options (like running a repair), I'm no expert. And before doing a reinstall I would give yourself more time to try other remedies before putting yourself through the dance. There's a wealth of info up under Tweaks, Guides, and the Acceleration Forums.