How to be sure to completely wipe computer of all traces of BC both previous and current version?

[ToussaintL'Ouverture]

Have run uninstalls, and also searched for files...but I understand there may be traces in registry and other places? any way to make sure all is clean, barring a complete windows reinstall?

[wudang_clown]

Have run uninstalls, and also searched for files...but I understand there may be traces in registry and other places? any way to make sure all is clean, barring a complete windows reinstall?

Formatting your C:\ partition is the best way to get rid of any unwanted files.
Now, to be serious, I would delete all SEGA entries in registry, placed in HKEY_LOCAL_MACHINE\SOFTWARE\SEGA. But I'm not sure, if it's safe, so do it on your responsibility!

[GrandViZ]

You do not need to erase the registry. Those entries will be overwritten anyways. Just run the uninstaller and you'll be fine.