GUID only ?

[blink41]

Hey !
I'm on the way to install my old leo distro (ipc) in order to get some informations needed for snow, but there is something that I actually can't understand : on every tutorial I've seen, there is always the need to set the partition scheme as GUID, not MBR. The fact is that I have some files on another partition on my HD (where windows is installed), and I was wondering if setting the partition scheme to MBR could be dangerous for my files...
Also, is there any way to install snow without a usb flash drive or usb HD ? I've seen there is a way with an hidden EFI partition, but haven't understoode anything...
That's all, Thanks in advance !

[x986123]

You can install snow using another partition. Create a 10gb partition, restore your image there, and install from there.

[updatelee]

The reason everyone recommends guid for SL is because the installer won't let you install on mbr.

[Ianxxx]

There is an altered OSInstall.mpkg file floating around that you can use to install on mbr