So long as you are using 8, you can use pretty much any hard drive you want. I've heard of incompatibilities with certain models, but for the most part that "incompatibility" has been user error. Seagate 40GB ATA 133 installed in my frankenstein 6200 right now running just fine. In fact, I don't think I have ever had an issue with 99% of seagate products. As far as a size limit, unless they sell 4TB 3.5" HD's yet, then there really isn't a limit.

EDIT: Didn't see that this was an old message, sry.