Given a small NT4 domain with PDC and one BDC, how do I migrate to
Windows Server 2003 when neither existing DC is capable of supporting
Windows Server 2003?

The recommended approach seems to be to upgrade the existing PDC to
2003, but the hardware on these boxes won't even begin to support that
scenario and that approach risks bringing the whole network crashing
to its knees with no way to back-out.

One solution is to install NT4 on a new box, configure it as a BDC,
promote it to the PDC, then upgrade to 2003, but I don't much like the
idea of creating a new server that's already stuffed full of legacy
NT4 installation files.

So what's the recommended approach? I'm an NT4 MCSE, but it's been a
while... so I'm looking for clear instructions but I know the core
stuff.