d:\dev>gem install extlib
ERROR: While executing gem … (Errno::ENOENT)
No such file or directory – \Documents and Settings\Melissa.BLACKY

meant “you need to be in the C drive”

the cause “for some reason ruby on this one box does an File.expand_path(‘~’) -> without a drive letter”

despite these settings:
d:\dev>set | grep HOME
HOME=\Documents and Settings\Melissa.BLACKY
HOMEDRIVE=C:
HOMEPATH=\Documents and Settings\Melissa.BLACKY

d:\dev>set | grep USER
ALLUSERSPROFILE=C:\Documents and Settings\All Users.WINDOWS
USERDOMAIN=BLACKY
USERNAME=Melissa
USERPROFILE=C:\Documents and Settings\Melissa.BLACKY