type hard drive supported by Apple TV 1st Generation
What kind of of a drive does it support?
SATA or PATA
The Apple TV is a digital media receiver designed by Apple and released on March 21, 2007
The answer is: A 2.5" PATA (=IDE) disk. Today (2012) they are somewhat more expensive dollar to GB than SATA and newer disk types, but they can be aquired most places, and often cheap, if they are used...
You could also buy an SSD (Solid State Disk) to minimize power consumption and build-up of heat in you Apple TV 1st gen. 64GB IDE MLC cost btw. $50 and 100. Possibly avoid the Chinese direct-to-consumer SSDs found on Amazon in bundles - Transcend's SSDs are also made in China, but at least you have a place to complain, if your's stop working.
SSDs of the type MLC are slower than SLCs, but at about 1/3 of the price of a type SLC. Cloning your old hard drive onto an SSD takes two partitions on the SSD, and this writing back and forth between the two partitions on the SSD are perceived by some as slower than using a spinning hard drive.
I replaced the broken original IDE-ATA disk with a 250GB SATA, adding a simple adaptor IDE-SATA. The only one problem is managing the space required by adaptor, I could not close completely the case , but this helps the air flow...
I also installed ATV Flash and now it all works great!!!