I would recommend 2 raptors for ultra fast loading time for your OS, applications and games that you play alot and then have an 80Gb drive for other games and music/files and things. If you cant afford this, 1 raptor will be sufficient and then have a 80gb drive for storage.
Two 7200rpm drives in raid0 are not going to be as fast a 1 raptor. You can see that this is true by looking at it like this:
The average seek time for a raptor is 5.2ms and standard sata 80gb drive is 9ms. Now if you put these two 80GB drives together, each drive is still going to have a 9ms seek time which means they will still be slower than the raptor. They are only going to benefit from being together in raid0 when you are copying lots of data which will mean you have 2 drives doing the work which should (but probably won't) half the time it would normally take to copy that data.
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