So you are saying that you have ONE IDE port with a cable that has 2 connectors and they are both being used by 2 CD Drives? Is this correct? If this is the case, then your solutions are either to buy a PCI IDE card or to go with SATA as you mentioned. No, you can't combine SATA and IDE drives on the same cable or port.
If you are using the machine for trading, SATA won't give you much of an advantage at current prices. I would examine whether or not you really need to CD drives and go with a much cheaper IDE, if you still have the option. It sounds like you have already made up your mind though.
I use the computer for tasks other than trading so I'll just get another hd. I think I got a good bargain for the SATA drive. I will probably build my next computer after knowing exactly what I want it to have in it. Hopefully I'll make enough money to build a computer for trading purposes only. Thanks for all your help. It has really clarified the situation.