Try this if one you want:
Run Mint's installer and in the partitioning section you should see all your partitions both Ubuntu and Vista (noted by sda1/2/3/4 or ntfs). By your post I assume you only have 3 Ubuntu partition, / , swap and /home (correct me if I'm wrong
Choose (double click) your / partition for ubuntu and tell the installer that you want this formatted and mounted as Mint's /
Do the same with swap
For your /home told the installer that you want the partition mounted as /home but DO NOT format it. Click Next and proceed with the installation.
I'm not a guru so this might not work very well for you, but I've tried this on my own and everything worked just fine