Alan, LuLu may want to make a Windows System Image as well as using Macrium. Two chances then if things go wrong
A little external hardrive is a great thing to have.
In case you are wondering what I mean LuLu I'm talking about a little thing like this which plugs into a usb port and has 500 gigs of space.
I am totally disagreeing with the need for a 32 GB or 64 GB Flash drive as previously suggested by Derek,
and feared that LuLu was going down that path with a "larger Jump Drive".
I did have in mind an external drive such as your suggestion of
WD My Passport Essential 500 GB Midnight Black Portable Hard Drive (USB 3.0/2.0).
For me the simple and reliable solution is a small Flash Drive to boot into Macrium WinPE Rescue with image backups on the external drive.
Macrium will cause no problem if the external drive also holds "native Windows Image files",
but since I do not trust the behavior of Windows I would be inclined to segregate the Windows images in a separate partition on that external drive.
My 2 cents:
I use an external usb 500 gb drive, has its own power transformer.
Up side is that its sturdier, doesn't draw power from the computers power supply, and usually cheaper than the newer smaller slicker ones.
Down side is that its big and clunky, must be plugged in, not very portable.
Doesn't matter to me, I don't need to haul all that software around with me.
You could put lots of backups on such a device.