Yes it is an older drive and it was working the last time I used it.
I had it in my old windows xp machine and had windows xp with a windows7 up grade installed on it.
If you think it's not being seen because it is a old HDD, I'll just buy a new HDD.
Not necessarily, I have an older one (basing on the capacity) and it works just fine.
Before you buy a new one, please consider these tips first.
1. Check the power cables, and the SATA/IDE connector. Make sure that these cables are working. You can confirm this by attaching these cables to a working HDD.
2. Check the HDD itself, like above, this time attach it to a working cable.
3. Do you hear any weird sounds on the HDD? If there are odd buzzing, or clicking chances are, your HDD is dead.
4. Do you have enough power to deliver to the other HDD? Please check if your PSU can handle another Hard Disk.
If after all these and the HDD is still not detected, well you might think of buying a new one.