First things first. In Windows Server 2012 R2 snapshots are now called Checkpoints. I may inadvertently call it either in this post. You should consider them synonymous.
Most of us who use hypervisors and virtual server guests have grown to love the ability to save a checkpoint before applying updates or performing a software upgrade. It's a great, easy way to have a clean place to fall back to in the event things don't go well. I had the opportunity to use a couple of checkpoints REPEATEDLY just this last weekend while I worked out why my Data Protector 8 upgrade wasn't completing successfully.
Usually checkpoints only last a very short while. It doesn't take long to work out whether the upgrades broke the server or the software installed correctly. But sometimes, rarely, you may happen upon a situation where you've got some checkpoints in place and you find that place where you've been saving them is running out of room. What do you do?
You should assume that deleting the snapshots isn't the answer your boss or Microsoft is likely to want to hear, though. You're keeping them for a reason.
But if you go and try to just move the snapshot location, even if the guest is turned off you're going to get a great big "you cant do that here".
Are there any options?
It turns out there are. Instead of trying to change the snapshot location you need to "Move" the snapshot storage location instead. It will move any snapshots you have, and hopefully (presumably) you'll have picked a place big enough you don't have to worry about running out of space.