I have encountered this same error in two different scenarios: The error message is a pop up box that appears when you try and boot the server. the message title is: Lsass.exe Access denied This has occured after I tried to perform an in place upgrade from windows 2003 server standard edition to Enterprise. I tried this twice on two different servers, one a DC, the second a recently demoted DC. The second scenario is having renamed the AD domain using RENDON (single domain single forest, only two dc's) I needed to rename the DC's, one at a time having juggled the FSMO roles, I demoted the DC's and removed them from the domain. When I bring the servers back into the domain and promote them, the error occurs again after the reboot. The error message appears in all safe boot modes as well. I am only able to run last known good, which restores the server back to pre dcpromo! Its happend on about 5 servers now. Any ideas?????