Hard Drive Suddenly Sluggish

Originally my system was one raptor sata and one ide 160 gig maxtor, both were fine but I needed more space. So I've added a sata 400gig hard drive, and done a clean xp installl onto the new 400gig (using the raptor only for games)....now the ide 160gig performance has dropped to unreasonable levels (managing a sustained write rate of around 5mb per sec)....is there any reason why this might be? perhaps something to do with having 2 sata and one ide? I'm at a loss....and thanks for reading!