Vista auto-detect on USB printers-- how to turn back on?

I had a HP 1215 photosmart printer that would be autodetected, but wouldn't
install because HP doesn't have a driver for it that will work for Vista. I
got tired of being alerted to this and chose the option to turn off
auto-detect for that device in one of the alert boxes, so I could look for a
way to get the printer installed (I later found out that I had to lie to
Vista and tell it I had a 7200 HP printer) . Now that I know the solution to
getting the printer installed, I can't get Vista to autodetect it again (I've
rebooted the computer and also unplugged and powered down the printer). I
also can't get it to autodetect another USB printer. It appears that
auto-detecting for USB port printers has been turned off permanently, which
is obviously not what I wanted to happen.

How can I get auto detect toggled back on? Thanks.