I am considering using a single 74GB Raptor for my XP and 2 - RAID 0 arrays (4x 150GB Raptors) plus one single 500GB drive for archiving completed projects. One RAID 0 array would be for reading the source video and the other RAID 0 would be used for writing the rendered files. Running Premiere Pro on a single drive under XP would there be any real advantage to this setup over a non-RAID four single drive setup?
It seems clear to me you've spent a while thinking this plan through, so I'm sorry to tell you that I think it's ill-advised. With modern hard drives pushing higher transfer speeds (up to 75MB/s) they nearly equal the performance of raptors, so throughput is not why you buy raptors, it's the low access time - 4ms versus the 8 or 9 of regular hard drives. This of course means they make blazing fast OS drives. However, using RAID arrays, whilst increasing throughput speeds (in the case of RAID0 anyway), actually harm access times. In short, you've pulled a very high transfer rate, but lost the one advantage to having a raptor in the first place. Additionally, the compromise of RAID0 is half redundancy. If one drive fails, you lose everything. The unfortunate problem with 150GB Raptors (not so for the smaller 74 and 37GB versions) is that they are unreliable. Between them, different friends own 6 150GB Raptors. 5 of them have become faulty within a year, not a very good track record. Normal WD drives are excellent for reliablity, as are the small raptors, but the 150s really aren't that great - Tom's Hardware Guide have withdrawn them from their test platform in favour of the regular WD Caviar SE16 drive for better reliability and copmpatibility with hardware. For this reason I recommend you ditch the RAID array and go with a Single 74GB Raptor for XP as before, but use three 750GB drives for your data store instead. Lower power consumption, higher storage space, lower price, lower noise level, lower temperature.
