I want to double my 300gb FSX drive by adding another 300gb drive and running them in raid 0. My question is can I set this up without disturbing the data? Or do I need to either backup and restore or reinstall from scratch?

You cannot do this without first backing up your drive via image (using a utility like Acronis True Image or Norton Ghost). You would then create the array, and then write the image to it.

I want to double my 300gb FSX drive by adding another 300gb drive and running them in raid 0. My question is can I set this up without disturbing the data? Or do I need to either backup and restore or reinstall from scratch?

Some advice to tune a system and FSX here http://www.simforums.com/forums/forum_posts.asp?TID=29041Way down this post you'll find info using Raid.