How to increase system buffer

Does anyone know a way to increase the system buffer in XP home. I can get great 12x burns but when it get to 12.5X the buffer craps out and the speed drops to 8x. The same on the rip, you can hear the rip slow and when the buffer increases the rip starts strong again. I have tried everything. The funny thing is that I have one drive that operate in UDMA 4 and it holds the buffer fine. All my other UDMA 2 drives have a problem. The drives themselves all have 2 mbs of buffer. My CPU should be good enough Intel 2.8 MHZ with 1 gig of Ram and 120 gig hard drive. Any help would be appreciated.