“I am still running Mac OS X Snow Leopard on a 2009 MacBook Pro with a Boot Camp partition that contains Windows XP. Can I upgrade to a more recent version of the Mac OS without losing that partition?”
In researching your questions I’ve seen reports of people having no problem at all – they download Mavericks, update their Macs and their Boot Camp partition works as well as it ever has. Regrettably, I’ve also read reports from people who can no longer access their partitions.
As with any operation where you can risk losing data, it makes sense for you to have a backup. That way, should something go wrong, you can restore your data. In the case of a Boot Camp partition this isn’t possible with Time Machine. Apple’s backup technology doesn’t support backing up and restoring these partitions.
Instead, you must turn to another tool. One option is to purchase a copy of Twocanoes’ US$30 Winclone 4. Once you have Winclone you simply create an image of your Boot Camp partition and tuck it away on another drive. If you then update Mac OS and find that the Boot Camp partition is no longer available you can create a new Boot Camp partition and restore your Winclone image to it.
The other option is to use a virtualisation application such as Parallels Desktop for Mac or VMware Fusion. With it you can migrate your Boot Camp partition into a virtual machine that you can run within the Mac environment. Operationally the advantage is that you needn’t boot into an entirely different operating system. Plus, the two environments can interact. You can, for example, easily move files between the Mac and Windows worlds. And these virtual machines can be backed up with Time Machine – no Winclone required.
by Christopher Breen, Macworld