Run Time Machine on same disk containing Windows files

I have an external storage device that's pretty big. I would like to store my OS X Time Machine backup files on it, but it already has a few files I've backed up from a windows machine. Will it be a problem to do both (File System wise), or should the time-machine work without problems? I don't want to lose any files already stored on the device. thanks.

Time machine requires HFS+ formatted partition to work. So you can:

• repartition drive separating it into two partitions
• reformat partition to HFS+ and use something like macdrive to access it from windows
• create disk image in this partition and use it for Time machine

Time Machine uses HFS+ to function and so by default won't offer the option of using a non-HFS+ formatted drive. However you can enable them manually by running in Terminal:

defaults write com.apple.systempreferences TMShowUnsupportedNetworkVolumes 1

Time Machine will then create a disk image that will live alongside your Windows files without needing to modify your partition at all. This is the same method it uses for SMB or NFS shares being used as Time Machine destinations.

Other alternatives as tig mentioned are to reformat or repartition your drive. I don't recommend making your own disk image (Time Machine will take care of it as I said above) as you need to make sure it's a .sparsebundle to avoid the 4GB file size limitation on a FAT32 formatted hard drive.