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I have an MacBook Pro with both MacOS and Windows 7 installed (via Bootcamp). I actually have to use both OSes every now and then. However, the apps on the Windows partition generate a lot more data.

Thus, I'd like to take 10GB from OSX and give it to Windows.

What is the safest way to do so without losing any data.

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up vote 3 down vote accepted

Well, there's an article that addresses this very question here. The short version is that OSX's Disk Utility is your friend. Use it to alter the size of the OSX partition, and then re-adjust the Windows partition.

Just remember to do a clone of your drive before you do so - you might just stuff it up, so it's always great to have a bootable backup. You can use a few different programs to do this; I've always used Carbon Copy Cloner. It used to be free - it now isn't - but comes with a 30 Day trial period. (As an aside, I've used this program heaps of times, and it's totally worth the price of entry!) SuperDuper! is another - never used it, but you can give it a shot.

Make sure you don't delete or alter your MBR! That's when booting issues happen - you'll remove your Mac's ability to find the bootcamp partition (hence the importance of the cloned backup - gives you somewhere to go back to!)

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Accepted. To add to this, you'll have to deal with OSX's Disk Utility clearing the data on the left side, rather than the right side. – AngryHacker Jan 6 '13 at 20:04

I would recommend booting from either the Parted Magic or GParted LiveCD/USB, reducing the size of the OSX partition, then extending the Win7 partition to fill up the unallocated space. If Win7 refuses to boot after this, you might need to run Startup Repair from the install disc.

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