2 hdd's 1 big partition

i have 2 500gb internal hdds that each have there own 500 gb partition. Can i combine these two into one big 1 tb partition

 

There's a couple of ways to do it, which might require backing up the data first, then combining the 2 hard drives.

1. Spanning the partitions with Windows. You'd have to convert the disk to dynamic.

2. Using a raid card, Raid 0, striped.

The risk is if one disk fails, the entire partition is lost.