Hi,

I am thinking about getting an external hard drive enclosure with an eSATA port.
My question is, is eSATA different than a USB/Firewire in that, I could install executable applications/games on the drive and be able to have it run?
Like, could I install a game on that drive and, to play it, I would need to plug in the hard drive?

Speaking of that, can eSATA ports be able to be plugged in and boot while O/S is loading?

On a hardware level the only difference between SATA and eSATA is an extra ground wire and possibly more robust SerDes. That's it. At the protocol level I don't think there are any differences at all. Unless you specify differently in software (which you should probably do to prevent caching from destroying your data) the OS will see the drive as a completely ordinary hard drive. It will be as any other device connected to your SATA controller.

Your questions are very confusingly worded, but the general answer is: anything you can do with an internal SATA HD you can do with an eSATA drive.