You are recording to the same drive you are gaming from.
You don't need raid0, you need a dedicated recording drive.
Get a WD blue or black and then use fraps to record to it. ie - dedicate the drive to recording. dont install programs or anything to it that might run at the same time as your fraps sessions. You want to avoid forcing the drive to try and do two or more things at the same time. HDD's are not good at this since they need to move the heads to another area. SSD's are awesome at multitasking thanks to the no moving parts.