Basically don't try to do it all in one step.
Upgrade the 4.5 in-situ first and then when you know it's ok migrate it to the new server.
This is the safest and most well documented approach to such an upgrade preserving the data.
Hello Rackroyd - I forgot to mention- the original and target box are the same.
1. The current server needs to have its OS upgraded to 2008 R2 from 2003
2. The current server needs to have its EPO version upgraded to 4.6.6
So there wouldnt be two servers at any point in time, leaving me to plan a very unlikely peaceful upgrade.