Which hard drive enclosure should I buy?

I just extracted the hard drive from my desktop, which has been unused for 2 years now. I want to place the hard drive in a enclosure, but I am not sure what kind to buy. The enclosure available in Best Buy have keywords like PATA, ATA, EIDE.

Are there rules I should follow when buying an enclosure?

The hard drive (40GB) was purchased in 2001.