In MOSS 2007 to SharePoint 2010 migration, got this Preupgradecheck issue: The following web part(s) are referenced by the content, but they are not installed on the web server
Solution: Enumerate all web parts and find the missing ones. Remove the faulty web part from the referenced pages. To enumerate all web parts, Run this STSADM command line:
stsadm.exe -o enumallwebs -includewebparts
Open the report it generated, search for “Missing”
Open the referred pages in Web Part Maintenance mode (append “?contents=1” to the end of URL. E.g. http://sharepoint.company.com/sites/sales/reports.aspx?contents=1) and delete those faulty web parts!