Hello,
2005 Express is not supported iwht 5.x http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=2006706, so have your DB migrated to 2008, have a look at the article.
- I have followed this and found it worked
- Take a complete backup of the DB (BAK format)
- Install sql 2008 express
- Restore the backup
- Create a system DSN point to the DB
- After installation of SSO, point the DSN to install vCenter.(After SSO installation, the vCenter installation will start).