Fortunately, my company is enrolled in a 6 year microsoft subscription. This probably sounded appealing when Microsoft partners gave their speech (a year before they had a dedicated IT professional). I admit that it is nice to have a server license with the ability to upgrade to the current version at the time of my choosing. A company definitely saves money over time. Anyheuw, thats what I did. I have a single forrest with one domain.

The domain I inherited was originally a windows 2000 domain. This became obvious after examining the selected options and functional levels. Apart from these inconveniences, upgrading from 2003 DCs to 2008 DCs was a snap. Important: You will need to raise the forrest and domain functional levels to 2k3 native to do the upgrade, unless thats where your forrest/domain is now. Windows 2k3 forrest/domains are in a Win2k compatibility functional level by default. Make sure to give your functional raise some time to propagate.  

After my forrest and domain functional levels were raised, I moved all 5 fsmo roles to a single "virgin" 2003 DC that was born for this adventure. This served to eliminate possible third-party/previous install conflicts.  Domain controllers seem to become a slave of small third-party semi-important services on a small Windows domain = too many on mine to think about fighting with.

Next I did a series of health tests on my Active Directory. I used Windows 2003 support tools to out put a series of tests' results to text files and studied them a bit. The Event Viewer is also helpful when improving AD health.  Upgrading to a new AD schema wont improve existing AD problems, it will only complicate them. At the very least, make sure that dcdiag and netdiag tests all pass and fix the event logged errors on your DCs.

After AD was healthy and all controllers were synced up, I put up a new 2k8 server and joined it to the domain. From my newly created win2k3 box, I prepped my domain for 2k8 

1. Insert Win2k8 DVD (either x64 or x86 = depending on what the "virgin" 2k3 domain controller is) and copy the adprep folder (on the DVD its \sources\adprep) to the HD
2. Upgrade AD definitions in the forrest: cmd to the root of the folder you copied -> adprep.exe /forrestprep
3. Allow the domain to take advantage of what the forrest has to offer: stay in cmd -> adprep.exe /domainprep
4. Upgrade the group policy to match the newly updated AD schema of the domain: adprep.exe /domainprep /gpprep
5. Optionally allow for read only domain controllers: adprep.exe /rodcprep