I have recently bought a external SATA hdd caddy which is usb and esata, I placed my old 500gb hdd in it and it works fine on usb but not esata.. but I suspect its my fault in that I haven't connected up my front facing esata port to my motherboard
Is there a special place it connects too or is it just a normal SATA port..
You will have to go into the BIOS and set the port you are using up to AHCI so that you have access to hot plugging and other advanced features. Your caddy will probably need an external power source too.
As long as you are not using any older drives you will get better performance by setting them to AHCI anyway. The only problem you would have is if you already have Windows installed on the drive and you change it from IDE to AHCI mode you would have to do a bit of registry hacking otherwise it wouldn't boot properly.