First clue to limit your server list: You are not allowed to load QC-sync Server on the same PC as QC Server is loaded on.
Next, try taking a guess at the QC-sync version you have based on the QC version.
Then load that version of the QC-Synchronizer client (get from HP's site).
Launch the QC-Sync Client and take the user/pass defaults when it tries to login, but point it to various Server names.
If there IS a QC-Sync server there, it will tell you so in the error, and will tell you the version it wants.
If you guessed correctly, it may let you in with the default user/pass.
Then, select the links and make sure their SCHEDULING tab has scheduling OFF -- they will still be able to run (possibly depending on completeness of the link with mapping, rules, etc.), but will be in a MANUAL state.