If you've had a disk fail - the data is gone.
If the array has died then you can probably recreate the array and not initialise it (using the same settings) and get back up and running. I've also used R-Studio to drop disks from an array into another machine and recreate the array that way.
If it's simply that the OS install is damaged, then provided the array config is intact you can Boot CD it fine.
It's pretty much the same as a single HDD. If the disk dies, the data is gone... but with RAID0 you have more drives so more chance of failure, if the OS dies the disk should still be accessible.
Simply solution is to either backup regularly, or not use RAID0 for anything you can't afford to lose.
