If you convert successfully a remote source machine that runs 64-bit Windows Vista, Windows Server 2008, or Windows 7 operating system and then try converting it again, the conversion fails with the error message Converter Standalone Agent installation failed on x.x.x.x Error code: 1603, where x.x.x.x is the IP address of the source machine.
This error message might occur if automatic uninstall of remote Converter Standalone agent has been enabled during the first successful conversion.
Workaround: Restart the remote source machine and try running the conversion task again.
Below there are two links which can help you out ;- http://www.vmware.com/support/converter/doc/conv_sa_43_rel_notes.htm
http://www.msigeek.com/715/how-to-troubleshoot-the-error-1603-fatal-error-during-installation 