Using PowerQuest's Drive Image 7 (now Symantec's
Ghost 9), I found that the folklore of
comp.sys.ibm.pc.hardware.storage to be true,
at least for Windows XP:
After cloning one hard drive to another,
disconnect the old drive before booting up the
new drive for the first time. If you don't, certain
features of the new OS become dependent
on the continued presence of the old OS. After
the new drive has booted up for the first time,
subsequent boots of the new drive can include
the old drive - which will be seen as just a file
system on a "local disk".
*TimDaniels*