I have an old PC that uses ATA100 Western Digital Hard drive. He said that as long as a hard drive in ATA100, then it would work with my PC. I know there are different pins and types of harddrives, so do you think this is true? If I do a search for ATA100 Hard drives, I get all different types, that's why I ask. I want to upgrade my Hard drive, that's why I ask. And no I do not know what kind of motherboard I have, and I do not have the manual. I am just curious to know if the guy was right when he said that all ATA100 HD would work with ATA100 motherboards. Thanks

How do you know you have ATA-100 when you say you have an old computer. ATA-100 is fairly new (less than 2 years old). What color connector is on the motherboard? The color tells you if it is ATA-33, ATA-66, or ATA-100. Look at the motherboard for text to let you know what brand and model it is. Boot up and look at the logo screen. The text in the lower left corner will tell you what model you have.

I spoke to a Dell tech and he said that I have ATA100, but that is all he really knew about that. I think my cables are light grey or white. Anyways, is it true that all ATA100 Harddrives could work with ATA motherboard? Or are there more factors to consider.

If your mobo only supports 66mhz, an ATA hard drive will just run at 66 speed. It's all backwards compatible, don't worry about it. Just get an ATA 100.

So in that case, your saying a ATA 133 Hard drive would work at 100 speed on a ATA 100 motherboard then right? (sounds confusing) Thanks :)