Great article for fixing pre upgrade related issues: http://sharepointreporter.wordpress.com/2010/07/30/fix-pre-upgrade-check-errors/ One thing to add.  Use the query here to find the name of the pages that contain the offending webparts.  I thought deleting the page would make them go away, but I was wrong.  I had to recover the pages that I deleted from the recycle bin and then open them in web part maintenance view (appending "?contents=1" to the url and then delete the webparts from the page.   http://surfpointtech.com/2012/06/28/how-to-find-a-sharepoint-webpart-name-from-the-id-or-guid/  Here's the STSADM commands: STSADM -o preupgradecheck and this one to find the sites that the webparts live in: stsadm -o enumallwebs -includewebparts > i:tempwebparts.txt Better yet, use the SQL command above to get the actual page that the webpart lives in.  

SELECT DISTINCT D.SiteID, D.WebId, W.FullURL as WebURL, D.Id As DocumentId,                  D.DirName, D.LeafName, tp_ID As WebPartSK  FROM       dbo.Docs D WITH (nolock)   INNER JOIN dbo.Webs W WITH (nolock) ON D.WebID = W.Id  INNER JOIN dbo.WebParts WP WITH (nolock) ON D.Id = WP.tp_PageUrlID  WHERE WP.tp_ListId Is Null AND WP.tp_Type Is Null AND WP.tp_Flags Is Null        AND WP.tp_BaseViewID Is Null AND WP.tp_DisplayName Is Null         AND WP.tp_Version Is Null  AND WP.tp_WebPartTypeId='<your web parts id>'  Source for this query is Ryan's comment her: http://stackoverflow.com/questions/1498409/sharepoint-find-where-webpart-is-in-use