|Trying to use a second HD - presumably with XP installed on it - is not likely to be successful; unless that drive and the OS installation were made originally using that same system...|
What happend prior to the problem arriving; did you install anything - software/updates - even hardare??
Meanwhile... get yourself a copy of knoppix or ubuntu (linux variants) and boot with that. Then go on-line and run a full on-line virus scan via Trend.com - using their freebie "Housecall".
"Anything" quarantined locally - delete it.
knoppix.com, ubuntu.com both have free .iso which download and burn to a dvd; boot with that dvd...