Complete Migration of files, programs, & OS from Laptop HD to New larger HD?

I am upgrading some laptops; memory, larger hard drives, etc.,.The laptop hard drives have mutiple partions (Dell OEM/Restore, Diagnostics etc.,) I got a good deal on hard drives with USB external HD enclosures.
Problem: What’s the best way to migrate files, data, programs and OS from the smaller old drive to the New larger drive with no problems. I thought I could just “GHOST” them and swap drives. I would then just use the smaller older drive as extra USB storage, but some one said it would not work with “GHOST” and have the new larger drives still be bootable because Windows OGA would not recognize the newer drive as same equipment? Can some one help before I go through all those hours of ghosting and it not boot up? :-
I’m running Dell Lattitudes D820 with 1Mb , Win. XP Pro. SP3 with 60GB HD currently…upgrading to 4Mb mem. and 320GB HD. All programs and OS is legal with no current OGA problems. with all latest updates, patches etc., and Comodo Internet Security complete. any aand all help would be appreciated.
Thanks in advance,