Kurt Shintaku's Blog

Another useful Technet Magazine post: “Find Upgrade Issues Before Upgrading to SharePoint 2010”

SharePoint Server 2007 Service Pack 2 includes a new Stsadm.exe operation preupgradecheck. Pre-upgrade check can scan your existing SharePoint Server 2007 environment for problems that may prevent a successful upgrade to SharePoint Server 2010. It is not a best practices analyzer, but it does provide a wealth of information about your server farm. It processes rules and scans your current environment, outputting results to %CommonProgramFiles%\Microsoft Shared\Web Server Extensions\12\Config\Preupgradecheck.

Many potential issues that might otherwise be missed—such as custom field types—will be reported by the tool. But unlike the process of upgrading to SharePoint Server 2007, upgrading to SharePoint Server 2010 does not require the tool to be run. However, you should always run the Pre-Upgrade Check tool before upgrading.

Read more here:

• Find Upgrade Issues Before Upgrading to SharePoint 2010
  http://technet.microsoft.com/en-us/magazine/gg271241.aspx