It should be available to change in the bios, check your manual. The only issue I can see is that when you remove the RAID 0, you will have two hard drives with little bits and pieces of your data and operating system on them (assuming your OS is installed on them). These drives are now useless and must be re-formatted. Sometimes companies don't ship their computers with full versions of the OS. Even scarier is that sometimes the OS disk is written as an image to the hard drive (this saves the company money because they don't have to make CDs). If these are your only two drives, you will want to make sure that you'll be able to install the OS.
Oh, and I can understand why you'd want to remove RAID 0. I've heard that it only gives you about a 30% increase in efficiency for most applications, and it doubles your risk of data loss.