Can't not use external hard drive!

[coors68]

Hi, there.
I have 5 internal hard drives as a scsi drive(c)-18gb w.adaptech scsi adapter and 4 IDE drives(200gb, 40gb,40gb,80gb w/promise ide controller).
I took out the 80gb had drive and put into the external enclosure(usb2/firewire combo) to use as a backup drive and potable drive.
But it did not work property.
When I turn on the power, computer show the external hard drive. It seem to fine, but during the coping, just stuck and nothing happen moment and erro occur.
Like can not copy to this hard drive .....use another drive something like that...
Then drive letter disappear. I was try so many times, but
same happend to me.
So i refomatted hard and low level formatted.. run diogonitic(?) something utility... That was fine..
So I thought it was external divice prob, but my usb pen drive(512mb) and ipod(firewire) are fine to transfer and everything...
Any1 has any idea what happen?
Please help me..
Many Thx... And sorry for my bad eng.
1.4ghz.(1.58ghz oc)-AMD.
1g ddr ram-266
a7a266 mb.
18g 10,000rpm cheatha scsi drive for system
adatech scsi controller
200g wd ide hard drive
80g wd ide hard drive
2-40g wd ide hard drive
scsi 32x cd rom
ide plexter 24x10x40 cd writer.
ide zip drive.
That's it!

promise ide controller

 

[RAG3]

I had an external usb2 hd and had problems--erratic on and off type problems. I would check power supply to external drive and the usb port on computer.Also I had problems using drive in a usb1 port.
Anyway I went back to a usb1 external box and no problems.