When I installed mavericks on my current PC, I made a 50GB partition on my hard drive (With an SSD for Windows) which was not formatted for the OSX installation. When i got to the disk utility settings I formatted this 50GB space with the "Mac OS Extended (Journaled)" from the tutorial here: http://www.macbreaker.com/2014/01/install-osx-mavericks-on-pc-with-niresh.html
When i finally got the OS installed, I let it update ect and use it for about 5 mins, and restarted back into Windows 7. From here going to My Computer, i noticed that i couldn't access my Hard drive and from here, All i could think is that the OS installation formatted my whole HDD loosing important data.
I managed to repeat this process with no important data that could be lost on an old PC with a 500GB for the current windows and made another 500gb partiton (which too, did not get formatted until disk utility setup) for OSX and this PC used 1 HDD and got the same results, the whole HDD got wiped.
I managed to install windows 7 on this old pc no problem with a OS selection screen on start-up, but what can I do to stop this happening in the future? (apart from buying a seprate HDD), as my friend wants to dual boot windows with OSX.