Today on a customer site I had to upgrade the vCenter Operations Manager to the latest version.
The problem was that the password of the admin account was not known.
After some research on the internet (google is my friend) I found a VMware KB article that describes step by step how to recover.
The VMware KB number is 2013358
We had already vCenter Operations manager 5.7 running but the resetadminpwd.sh was not on the machine. I had to follow the steps as described for version 5.0.
Hope this will help you.