upgrade to v10.7 first and then to 11.0.1. See the upgrade paths listed here. 2003 is still a supported platform for NPM v11.0.1
SolarWinds Knowledge Base :: Compatibility of SolarWinds Orion Products for Installation and Upgrade
SQL server must be 2005 SP3 minimum for v11.0.1
from the customer portal, de-activate the license on the old machine (there are instructions in the admin guide)
disconnect the old server from the network.
assign the same computer name and IP to the new server
run the v11.0.1 installer, and choose the SQL instance + DB that was used by the old NPM server. Use the NPM license that was de-activated.
As always, backup the database and servers before doing any upgrade step
There is also a formal document here - http://www.solarwinds.com/documentation/orion/docs/OrionServerMigration.pdf