Mirrored means that both drives are working together on the same files, but one is copying the other. That's actually slower and not really the best option for editing. Do you have your system on those drives, or is on a third drive, using a different buss?
Raid 0 (stripped volume) is much quicker and can be done via software in windows. However, you'll lose all your data is one drive fails and should only be used for video. Install your system onto a separate drive.
I use a RAID 10, which is both stripped and mirror. It's four drives set up as two raid 0, where raid one copies the other. Should one drive fail, I have a copy of the data on the other to recover from. I have those on an LSI MegaRaid card, and with 6 GB data-rate, I have plenty of head-room for fast disk speeds. (However, I do have two old Dells that still use a 2 drive RAID 0 via windows, and have not experienced any failures). I tend to replace the drives after three-years of constant use to head off any failures. I never fill them past the 50% mark, and always archive finished projects to an external drive.
When I built my latest machine, I ran into a hardware conflict with an AJA capture card. I looked up the mobo spec and found both slots shared the same resources, so I move the card to another slot to correct it. I also had issue with a sound card sharing IRQ with the USB ports. Every time I plugged a drive into the USB port, I would experience audio glitches. I solved that by disabling the card and using a USB Mixer that came with its own ASIO drivers. In that case, I simply rolled with it (as disabling the USB was not an option for obvious reasons). Think of your PC as a busy highway with lots of intersections and ramps, and the DATA as the vehicles. You want to keep the fast devices in the fast lane and out of congested traffic. Does that make sense?
If you do change your hard drive/raid configuration, copy your data to a storage drive first.
To recap: At the very least, install your system onto a separate drive. Use another drive just for video, and make sure that video drive is not sharing resources with slower devices. If you want something faster, then use two drives for video in software RAID 0. Still faster, use a dedicated RAID card to control them.