I believe a single 10,000 RPM harddrive would be your best.
1. RAID 0 really doesn't improve performance much in a single user environment (atleast that's the opinion of Storagereview.com
2. 8GB's ain't a whole hell'uv a lot of room. If it's the same price for 8GB flash drive or two large harddrives....you're paying unreasonable premium for speed. Also take into consideration that flash memory can only be rewritten so many times. While most of us would never notice this with our flash drives because the number is indeed VERY high....having an O/S with a paging file on a flash drive constantly writing and re-writing might not make the flash drive last that long.
Get a 34GB, 74GB, or 150GB Western Digital 'Raptor' drive.
Get a Raptor 150 and call it good or they have some good deals right now on the 74gig at bestbuy for 119.00 this week, which is as low as I've seen it. Either one will perform extremely well. The difference in loading a game with raid 0 and a single raptor is about 1 second. Hardly worth the additional problems striped array brings with it. I have 2 74 gig raptors and 1 36gig raptor, setup as single drives, and am very pleased with the performance.
As far as a 8gig flash, you could load a game on it but it's really too small to load more than about 1 game given most games now are around 5gigs and getting bigger. I don't know if solid state hard drives will ever really take off given the growth rate of Operating Systems and games, I would be surprised if it ever becomes a viable alternative.
I would 'think' this would result in the same speed as single harddrive. I can't prove that, but any speed you gain off of RAID 0 would be lost in the RAID 1 parity. It's a nice setup for mission critical storage so that if any single harddrive failed you would loose all your data...but that's not going to help you. RAID 1 and RAID 5 SLOWWW things down--that's the cost making sure a harddrive failure won't result in a lost of data.
Follow mine and cisco's advice: Get a 10,000 RPM drive. Forget about RAID 0. I know all the cool kids have a 'RAID' on their system....but it will not dramatically increase your speed (as shown in the Storage Review article).
You may think that 37GB, 74GB, or 150GB's isn't a whole lot of space. 74GB is PLENTY for installing an Operating system and MULTIPLE games. For all your Music, Movies, Data (game patches, images, etc), get a second, larger but slower, harddrive. 320GB 7200RPM drives are $90 on newegg. A 500GB 7200RPM drive is $150 on NewEgg.