wow, you certainly went overboard with the memory!!! Windows XP 32 bit does not work very well with any more than 3GB of memory.
i guess you really haven't used 3Dmark before. i don't know why you would be concerned because frame rates are low. it's a benchmark, not a game. game performance is all you should be worried about. 3Dmark is designed "ahead of it's time". each previous version has been known to give graphics cards a good run for the money for 2-3 years after it's release. the whole idea of 3Dmark is that it puts an insane amount of stress on your graphics cards. no offence, but seeing as you don't seem to be a benchmarker i have no idea why you would even choose FPS to guage performance in 3Dmark. the only thing that even comes close to mattering is the 3Dmark score at the end.
summary: 3Dmark is only useful for boosting your ego
only the performance in your games matters.
i can't help with your question about RAID1, do you understand the various levels of RAID though? also you will need to partition and format the second drive to be able to see it in windows, don't worry that is a VERY common mistake.