Problems with Altera Quarus 5.1 on Vista

Are you using version 5.1 because you are updating an old design that was done with that version? If you don't specifically need to use the old version, you will probably be better off using the latest version. Many major feature additions, enhancements to old features, bug fixes, etc. have been made to Quartus between versions 5.1 and the current version 7.1. Version 7.1 is available on the Altera web site for download of either the subscription edition or free web edition.

Even though Vista is not officially supported by version 7.1, it would have a better chance than 5.1 of working.

I don't think Altera claims that Quartus II supports Windows Vista (yet). Here's the OS suuport table that I found on the Altera web site:

http://www.altera.com/products/software/products/quartus2/os/qts-os_support.html

It looks like you're going to need to find a Windows XP, Windows 2000, Solaris, or Linux machine.