I have a domain with a PDC server and a BDC server. I want to replace the PDC, where I have Exchange 5.5SP2, with a bigger server and basically maintain the same names and Exchange settings. How can I do this?
Hmmm...if you really must have the same names, then your situation is a bit more complex.
Your best bet will be to get a full set of backups of your Exchange server (Online and Offline), down your PDC (don't dismantle it yet, though), promote your BDC to a PDC, then install the new PDC as a BDC with the proper names and all. Install Exchange on there, and then do a full restore of your off-line backups.
I encourage you to read the Microsoft Exchange Disaster Recovery White Papers before you begin, so that you're fully familiar with the issues of backing up and restoring the Exchange server.
When you do your restore, restore only the Exchange Data—not the NT or Exchange application stuff because that stuff likely will be a bit different on your new server. Also, you need to restore to the same pathnames as you had on your old server. You can move them later, if you have to.
Once all of that is done and you've verified that your new Exchange server is working properly, you can promote that machine back to a PDC (which will revert your old BDC back to that role) and you should be in business.
As always, make sure you have good backups and leave the old machine intact and ready, just in case something goes awry and you need to bring it back up until you can troubleshoot.