That's what I did . . . as FedoraRefuge has said:
I had a triple boot . . . Vista, Ubuntu and LinuxMint.
I saved all files, backed-up everything and did a complete install of LinusMint-7 (Main)
Deleted both Vista and Ubuntu, partitioned the complete hard-drive to LinuxMint.
Easier than deciding, should I make that partition this big or maybe make another partition for . . . ?
Also, read in the (LinuxMint and Ubuntu) Forums, that upgrading or using a re-partitioning manager can sometimes cause more problems.
Better and easier if you could do a 'fresh install'
Have not encountered a single problem with it .... m'thinks, I made a wise choice.
Maybe, in the future, after I try out LinuxMint-8 Helena, for a while ... I'll start "distro hopping" ... but for now, I'm happy with my OS.