You're on the right track here matey, but it didn't work when I tried it ... However, I've got Vista on a Seagate EIDE, Mint 5 on a SCSI SATA and BusyBl**dyBox doesn't like it! - I can only talk to you now with Minty Freshness, with the Vista HDD physically disconnected ... Ho Hum ... "ide=nodma" just made Minty hang in limbo ...
Are you saying when you disconnect the vista drive Linux Mint boots up and runs just fine? If so what is your root partition labeled as (in the grub boot options, like root=/dev/sdaX) upon a successful boot?