Last month, I was attempting to install Mint4Win (Mint 9) on my desktop, where Win 7 Pro (64 bit) is my primary OS. I do have a full install of the 64 bit version of Mint 9 on an external drive (320GB), loaded with data (VM's & such). I was just wanting a simple way to access Mint fast, w/o plugging & booting into the other drive.
I attempted the install 3 times, the first 2 times w/the 32 bit version, the last w/the 64 bit one. My data partition was wiped out, to the point that Windows 7 didn't see it as a partition, but unused space. Fortunately, I had the presence of mind to backup (as I always do) prior to making a major change.
However, I installed the 32 bit version on my wife's notebook computer, for when we travel, and it works perfectly fine.
I'm also a 2 year user of Mint, it's the best Linux OS on earth, as I've already stated, I have another install, on it's own drive, and while I'm still learning, I'm no longer a "newbie". I consider myself an intermediate Mint user (need to work on using the command line more).
Also, I'm simply reporting this a possible bug, as I won't try this again on here. More or less a warning to others to backup before attempting this, too. What I done for when I want quicker access (actually a better solution) was installed it inside of VM Ware Player (free version).