Hi,
Have you just re-installed the vCenter or did you re-installed SSO, inventory , vSPhere web client too. Also are you using default certificate or CA signed certificate ?
If it is default
1. First take snapshot of virtual machine where you have vCenter server and other component installed
1. Re-install SSO
2. re-install vCenter and register to this SSO
3. re-install Inventory and register to SSO
4. Re-install vSphere web client and register to SSO
Here is Kb for register it from command line http://kb.vmware.com/kb/2033620
However while doing re-installation , it will ask you to register it.
Regards
Mohammed