ALL GPT formatted drives have a "Protected MBR" defined to prevent incompatible OS's from trying to write to them.=20 The following might help with any other questions. http://www.microsoft.com/whdc/device/storage/GPT_FAQ.mspx Alan Melia t: 0118 977 4963 m: 0781 771 0060 w: www.melmac.co.uk -----Original Message----- From: Josh Koffman [mailto:joshybear@gmail.com]=20 Sent: 01 February 2011 20:40 To: Microcontroller discussion list - Public. Subject: Re: [TECH] Can a Windows PC Read a drive with a GUID Partition Map= ? On Tue, Feb 1, 2011 at 3:01 PM, Nathan Nottingham wrote: > http://en.wikipedia.org/wiki/GUID_Partition_Table#OS_support_of_GPT > > http://refit.sourceforge.net/myths/ > > In short, you need a MBR for viable Win32 compatibility. =A0Your Mac will gladly boot from a MBR, however, so sticking with MBR won't hurt. =A0The OS= X installer just refuses to install on a drive without GPT. Interesting. I'm using "Carbon Copy Cloner" on the Mac to do the cloning, it flagged the drive as being a potential problem as a boot source for OS X. Thanks for the info! Josh --=20 A common mistake that people make when trying to design something completely foolproof is to underestimate the ingenuity of complete fools. =A0 =A0 =A0 =A0 -Douglas Adams --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .