I'm really not sure about all of this ... ON YOUR OWN HEAD BE IT !
Please bear in mind we are in 'uncharted terroritory' here ;)
If you don't turn off system restore windoze will very helpfully load up your 'last known good' registry & so replace the one you just 'tweaked', because only 'on setup', should have a 'no hardware' set, and unless you add the reg key that fires that bit up it'll decide some corruptions taken place & start doing its 'thing' - but we don't want to add that key because we don't want it to zap all our previously installed proggies ...
Here's some registry backup/restore instructions (I only had a very quick glance!)
The console tool for registry revovery is Bill's brother 'reg' :)
I really think we could have done a complete fresh install & added back all your proggies by now, AND BE SURE IT WOULD WORK !
All this may very well not, infact I'm pretty sure its gonna break!