OK, this is some IDE hardware advice.
Most motherboard that with a PII or later, and all hard drive over 10GB are ATA 100 capable, 100 mhz data transfers. Early motherboards and hard drives are ATA 33, only 1/3rd of ATA 100.
ATA 100 needs 80 pin cables, yet some new systems from shops and major suppliers have ATA 33 (40 pin) cables.
Two devices on the same cable will both work at the speed of the slowest device.
About 95% of the PC CD and DVD drives are ATA 33. Many shops mount the CD/DVD as the Primary IDE Slave, thus slowing the hard drive access down.
The best performance from a modern IDE system is by using two or three hard drives and a CD that are all ATA 100 compatible. You set up the Primary Master hard drive as youroperating system, the Primary Slave hard drive as your Applications/Programs disk, and the Secondary Master hard drive as your data store, with the CD as Secondary Slave. All ATA 100 compatible with 80 pin cables. If only two drives set up the Primary IDE as above and put the data on either one.
When you run an application the system can access all four devices at once instead of hunting over the one hard drive switching from the operating system to the application to the data, as it needs to access different parts of each.
This will greatly speed up the performance of most systems, and works on any system. The use of 3 hard drives will actually give a better operational improvement on slower systems (ATA 33 or ATA 66) or those with big hard drives.
BTW The only inexpensive ATA 100 IDE CD that I have found is the ASUS E616 CD/DVD player.