I had the same problem as vikassethi. However, I had to uninstall asp.net as an additional step before installing asp.net 2.0.
This resolved the issue.
I just installed Vault Professional. When visiting the Admin Web Client (i.e. http://{serverName}/VaultService/Admin/) I get the below error. Note: I get similar error at http://{serverName}/VaultService/VaultWeb/Login.aspx I assume there is something wrong with IIS (v 5.1 on XP pro) setup. But, I d...