|If you look on eBay there are many reputable sellers selling IDE hard drives from corporate disposal PCs.|
There are still some available new from retailers for the spares market.
One IDE port can be used to run two IDE hard drives.
You can also buy add on PCI cards which will allow you to run IDE or SATA hard drives. These cards are not very expensive either.
Here is an example:
You can also buy external USB based hard drives if it is just storage you want.
This is feasible if you have USB ports. If you dont have USB ports then you can also buy PCI add-on cards to give you some USB2.0 ports.
These external drives can be quite high capacity too.
Example below £35 for a 500 GB drive:
You can buy these from other retail and direct outlets such as well in addition to eBay.
☺ When everything else fails, read the instructions.