Using three Hard drives

to use a HDD and a cd/dvd drive on the same cable, you are asking for trouble. I have gotten it to work before, but usually, 1 of the devices does not work properly.

A suggestion though. For the 3rd HDD, you have a few options. Try a USB drive bay, or pick up a SATA card and add it to your system

Sounds like you either have the wrong type of drive or you grabbed the floppy cable rather than the secondary IDE cable.

A lot of systems have just a single connector IDE cable for the CDROM drive. (Saves some cost) So, you may need a new IDE cable.

I myself have had no problems running a hard drive and an optical drive on the same cable.

In the past, there have been performance issues when mixing optical drives and hard drives.
Some older IDE controllers limited the data transfer rate to that of the slowest device on the cable.
Some older optical drives will not work with the 80 wire IDE cables required for ATA 66 and faster hard drives.

If you think you might want to add a 4th hard drive, or an additional optical drive, it does make a lot of sense to add a controller card. I do recommend going with a name brand rather than a generic controller card.

One other factor to keep in mind. As you add hardware, you increase the demand on your power supply and increase the need for proper cooling.
Make sure the power supply has enough capacity for all of your devices.
As to cooling, I like having enough filtered fans forcing air in to create a positive air pressure in the case. This both keeps dust out, and helps everything run cool.

Chas