I'm pretty sure support for Windows 7 only came in with 5.1. That's not to say that's your problem, but I'd start by trying the latest version. I presume you're needing 5.0 for compatibility with others in your organisation, are you? Otherwise I'd go straight to 5.2, anyway. At least if you install the later version you'll know if that's your problem or not - and if it still doesn't work you can talk to Tableau support.
I can confirm that we do not officially support Tableau 5.0 on Windows 7. You must use Tableau 5.1 or later.