<p>What is the best way to go about upgrading TFS 2005 to 2008? Also, what about the Team Build scripts ("Build Types"), are those compatible with Team Build 2008 or do they need converted/migrated somehow?</p>

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Upgrading TFS 2005 to 2008
I mentioned that the SharePoint upgrade to 3.0 was the main difficulty. I thought it was performed as part of the upgrade, but it in fact is a separate upgrade process. You should also install Team Explorer 2008 before installing Visual Studio 2008 Service Pack 1 on developer's machines. If you don't, you have to go back and reinstall the service pack. Also be sure to get the SP1 RTM version, which MS just release in the past week or so. If you have already installed the SP1Beta, then you have to download a special removal tool, run that, then install SP1 RTM. We did not have any custom build types, but we did use a custom build guidance package from Conchango - and it upgraded OK.