Please help with external HD

[jenkins24]

I recently bought an external hd enclosure and placed one of my unused WD WD12. It is a 120gb internal hd that i made with the new enclosure to be external. My problem is when i turn the hd case on, the computer will not recognize it unless I turn it off then back on. I'm sure this can't be good for the HD plus it is a hassle. I am using windows vista home pro. Please help.

[tempus]

Could it be missing the drivers for the external enclosure? Whuch brand enclosure is it and what is the motherboard you have?

[jenkins24]

It is an "Ultra Mini Portabale Disk Compact External Hard Drisk Enclosure." I'm not sure what MotherBoard I have. I have a hp meadia center m7470n.