Are my SATA 2 drives set up properly?

[compoundz]

I recently put together an Intel quad with these specs:
ASUS P5K P35
Q6600 2.40G 775 8M
3 Seagate HD 320G|ST 7K 16M SATA2 ST3320620AS drives
2 gb Crucial Ballistic 1gbx2
ZALMAN | 9500A cpu fan
ANTEC|SONATA III w/ 500 watt pwr supply
Windows xp sp2

I'm using this mainly as a Digital Audio Workstation. The rig is running great, but I'm wondering if the drives are set up properly. They're running in ultra DMA mode 5.
What happens when I go to record more than 60 tracks with a transfer rate of about 7-8 mb/sec (which it should do no problem) is that the amount of ram starts to shoot up until it eventually crashed the program and the audio is glitchy and the gui is lagging. It seems like the drive can't keep up.
If I use an old external firewire drive, I get 130 tracks with none of these problems problems.
It's odd because the Sata 2 drives benchmarked at an avg transfer rate of 65 mb/sec, where the external drive is at 29mb/sec.
Did I set thes drives up improperly? I used an nLited version of windows with the sata drivers embedded on this install.

Thanks

 

[compoundz]

Is this in the right forum?