Unable to boot computer when external USB hard drive is turned on.

I just bought a Seagate external 200GB USB/Firewire hard drive, and
connected via USB (2.0) to my a850e (with AMD Athlon 64 3400 cpu). I
used Seagate's Disk Wizard utility to partition the external drive into
3 "data only" - supposedly - partitions. Now, it works perfectly if I
turn on the external drive when the computer is already up and running -
plug'n'play recognizes it, and all is well. However, if I turn it on
before I boot up the computer, I get a message, after the initial boot
sequence screen, about "OS not found". I figure the system is trying to
boot off the external drive, and I've played around with the boot order
setting in the BIOS, and can't seem to hit upon the right settings.
Anyone have any ideas? TIA.

 

On the seventh day, Debbie the Dogged wrote...

you might try to disable the usb legacy support but since that disables usb
keyboards and mice in non-windows mode as well, I'd just disable the drive
for as long as the pc needs to boot up.

--
mit freundlichen Grüßen/with kind regards
Christian Dürrhauer, Institute of Geography, FU Berlin

Money, it turned out, was exactly like sex: you thought of
nothing else if you didn't have it, and thought of other things
if you did.