logical drive letter assignment- IDE and SATA

There have to be caveats that I am unaware of when installing a SATA drive and then adding two IDE drives to a desktop.
XP PRO
ECS-600A Motherboard
WD 160G Sata
WD 40GB IDE

What’s happening is the logical drive letter assignments are not in proper order.
The SATA drive shows as C, the NEC DVD Writer shows as D, even when the IDE drive is installed in the system…is it as simple as a jumper Master/Slave issue, or is there something else I am missing?

I’d appreciate some design/installation rules from the PROS!
Thanks in advance.

Chad