About 2 weeks ago, hubby opened the case & changed the master & slave on the burners. Since then the computer will start booting up & will shut down before everything has finished loading up. It always gets to where we can see XP logos, often the entire desktop. Sometimes it takes another 1 or 2 times, but it will completely load & will not shut off after this point unless you intentionally shut it down. He reopened the case & there are no loose connections, which was my first thought. The hard drive is older, so I'm wondering if it could just be time to replace the drive---or if it might be something else. We built the desktop within the last 6 months (I think), so the case, power supply, motherboard & processor were new at that time. Just thought I would try to get some input before we try anything.

Do you mean that you re-configured the jumper settings on the back of your CD drives or have you interchanged IDE channels with your hard drive(s)?

I am assuming the internal drives you are running, are doing so with an IDE interface?

If so, it is advisable to run your hard drive(s) on your primary IDE channel.....and your CD drives on the secondary IDE channel.
Interchanging this can lead to conflicts for resources within your system!
I may be way of track here, however your problem description sounds suspiciously like a resource conflict!

Hubby changed the settings on the 2 burners switching which one was master & which one was slave. He didn't touch the IDE settings. All drives are IDE.