You're old system was sold with the power supply for the options installed. Basically, that means they put a big enough wattage unit to handle what was there. Now being older it loses some of its pep over time. On top of that CDs tend to not last as long as some people expect, especially for the cheap OEM units, but that's my opinion. I suggest you either upgrade the power supply to a higher wattage unit. Plus, verifu you have a clean CD drive as well. Get your hands on a CD cleaner kit of some sort and use it now and then as well keeping CDs themselves smudge free. Verify your system fans are running OK and clean out system case, this will help reduce or keep the air circulation for its intended purposes.
good luck -----Willy
My system is HP Pavilion 6535. 500Mhz, Win98se. Only upgrade was ram. I have went through 4 cd drives in the last year. They quit working after about 3-4 months. The light will come on momentarily than flicker after you put a cd in the drive. The system is frozen until you open the door for the cdrom. If it does work it will read for awhile than quit. At which time I get the message, 'put cd....in drive and push enter or escape. Know anyway in which the computer can kill the cd drive? Or is this really bad luck?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic