More precisely, to use 48-bit LBA (for HDD's over 137 GB) with Win XP, it must be SP1 or later, not necessarily SP3. However, no matter how you start out, if you use XP, I definitely recommend you do the upgrade to SP3.
What version of Windows is already on your 80 GB HDD? IF it is XP original (no Service Packs) or earlier, you MUST update BEFORE making the drive upgrade. But if you have at least SP1 already running, or if your OS is Vista or Win 7, you have no worries. Wherever you buy your new HDD from, check the unit's manufacturer's website for a cloning utility. Both Seagate and WD have very good ones you can download for free, and they do a LOT more than just cloning. Seagate's is Disk Wizard; WD's is Acronis True Image WD Edition. With each there is a small trick to watch for in going to a much larger drive - you usually have to set the size of the new Partition on the new HDD manually, because the default often is to make it the SAME size as your old drive!.