Since this is an older computer with IDE ports, just how old is it? I'm wondering if you might have a problem with drive size. This can be a problem with IDE ports from around year 2000 and earlier.
First, what size is this old HDD you are trying to install? On older mobos that lack a feature called "48-bit LBA Support" you can NOT use any HDD over 128 GB (the way Windows counts) or 137 GB (the way drive makers label them). If your old HDD is smaller than this limit, you are OK no matter what. In that case, ignore the rest of this and skip down to my points about IDE jumpers and cables. But if it is larger, you MUST have the feature before trying to use the drive in the machine. If you don't you could destroy data on it.
How do you know about this? Read the mobo manual carefully, and / or the maker's website for features of the IDE port system. Just "Supports large hard drives", or "LBA Support" is not good enough. (The older system from the 1990's used 28-bit LBA.) It must specify "48-bit LBA Support", or a least support for drives over 137 GB. If you don't have that, but do need it because the drive you're moving is this large, your best bet may be an update of the BIOS. Search the mobo maker's website for a newer BIOS for your board AND for instructions (and maybe a downloadable utility) to "burn" the new BIOS to your mobo's chip. Look specifically for a BIOS version that says it adds 48-bit LBA Support. If you can get this, install the updated BIOS BEFORE you install the old large HDD and work with it.
NEXT you also MUST have 48-bit LBA Support in your OS in order to use any drive over 128 GB. The original version of Win XP, and any OS before that, did NOT have this feature. It was added in Service Pack 1 and maintained thereafter. So if you need this feature and you have any SP installed in Win XP, or if you have ANY version of Vista or Win 7 as your OS, do not worry about this. BUT if your OS is original XP or older, again you MUST update it with a Service Pack or something before you can use a drive over 128 GB.
Now, on to IDE jumpers and cables. There ought to be a label on the drive that shows you how to set its jumper. If there really is not, you probably can find the info on the maker's website using its model number, as you plan.
Once you have that, note these things.
1. The physical slot in the case where the drive is mounted means nothing. What matters is the way the drives are connected to their ribbon data cables.
2. On the Primary IDE port, you probably should arrange the drive with your OS (the one you boot from) as the Master of that port, and the second unit as the Slave. Set the jumpers that way.
3. On that Primary port, plug the Black END connector of the ribbon cable into the Master drive unit. Plug the Grey middle connector into the Slave for that port.
4. Set jumpers for the two devices on the Secondary IDE port similarly. BUT sometimes it is best if the HDD is the port Master and connected to the END plug. Then the optical drive should be the Slave on the middle connector.
5. Once these are set up, boot into BIOS Setup immediately and check whether all the units are detected properly. If one is not seen in the BIOS screens, it has a hardware problem.
6. When they are all detected, find the BIOS screen for setting up the Boot Priority Sequence. Most people would set to try the optical drive first, then the one HDD that has your OS installed on it. and NO other devices allowed.