I’ve just spent the past couple of days looking into the ‘upgrade’ process and I’ve come out the other side. Here’s a quick jot down of what I encountered

1. Environment: Single WFE (Win2K8 R2 x64) and a separate SQL 2008 x64 'backend’. Currently running SP2010 Beta2 with content databases around 13GB
2. I haven’t uninstalled any of the existing SP2010 beta 2 bits – this is a VM and I have a handy backup, so in case of emergency break glass was my plan b.
3. Launched Setup.bat – up came the intro screen and I selected Install PreReqs. In my case the prereqs failed their first installed with it grumbling about the IIS Web Role not present (but this was an existing SP2010 server, so obviously the Web Role was present and correctly running).
   
   Ran the PreReqs again and all was fine :)
4. Setup.exe – launched the product, provided a license key and we ran all the way through no problems. Interestingly thRege installer didn’t mention anything like “…I found a previous version of SharePoint do you want to …”
5. Configuration Wizard – this is where my trouble started.
1. As the Wizard was launching, it appeared not to be able to recognise the fact that we were already in a farm. It was like we were running on a machine, where the DB Server wasn’t accessible.
   
   I ‘removed’ the Server from the Farm (which were the only options in the Wizard for me)
2. Re-ran the Wizard Take#2, supplied the details at the beginning, Server Farm etc etc and sent it on it’s way.
3. The Wizard ran up to step 3 of 10 (where it configures the Farm DB + creates the SharePoint Web Services IIS Site) and then FAILED. What I noticed that the FarmDB was created successfully, but the IIS side was failing.
   (The error logs spoke about a socket based error – which I think was unrelated)
4. Tweaking, rerunning the Wizard didn’t fix things…so here’s my fix….
5. I also uninstalled SP2010 RTM a few times and reinstalled, but same error
6. The fix -
1. Delete the \14 hive
2. Delete the Registry Key (and all under it) HKLM\Software\Microsoft\Shared Tools\Web Server Extensions
3. Uninstall/reinstall the IIS Web Role on the Server
7. Repair the SharePoint install from rerunning Setup.exe – repair option. (you might be able to leave this step out, but I deleted the Web Server Extensions key after I installed SP2010, so I needed it to be rewritten)
8. Run Config Wizard
9. Upgrade any Content DBs you want to mount – through stsadm –o addcontentdb or Mount-ContentDB (powershell)

I’m sure you’ll be able to shorten this list of steps when you upgrade, but I’ve got to get on and configure this environment.

Have fun,

Mick.