It is quite possible to combine 2 identical disks into a raid0, but that means that all data will be lost when you format the drive(s). That does not make sense at this moment with all your rushes on the current disk.
What looks feasible is to add a 3rd disk and move all your project files, render and PEK files and media cache and scratch files to your third disk, clearing up room on the current disk and then defrag the disk.
One other thing to look at is your video card, the 6200 is rather old. Maybe upgrading will help to improve your performance as well.