External Hard Drive - Erase Content in Order to Back Up?

[leitmotif]

I have an older WD MyBook and I'm only using about half of its capacity. I don't know much about this sort of thing so I am here to ask for advice.

I went to try to do a time machine backup of my MBP and the program tells me I'll have to erase everything on my external HD because it has an incompatible file system. Previously I used the HD with my 2 PC laptops. As I said I'm only using half the capacity and now have 2 MBP's (mine and my wife's) I need to start performing back ups of these. Do I need to invest in another external HD? I'd like to avoid the cost if I can even though the HD I have is older technology and not the highest storage capacity, it seems to suit my needs, for now.

If purchasing a new HD is the best route, can you recommend a decent unit? Maybe 1TB and if it can be accessed via wifi between 2 computers that would be nice, but not a necessity.

Thanks. PS: I'm not familiar with a lot of technical terms related to computer so hopefully you can explain these things in layman's terms for my idiot self. Thank you again.

 

[Fishrrman]

"If purchasing a new HD is the best route, can you recommend a decent unit?"

Don't "lock yourself into" another external HD in a case for backing up.

Instead, consider one of these gadgets (can you afford $25?):
http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias=aps&field-keywords=usb+sata+dock&x=0&y=0
(many items shown, they all work the same, pick one that's cheap, a USB3-equipped unit would be your best choice).

Then, buy a "bare" SATA hard drive from the vendor of your choice (perhaps you know someone who has an old one just "lying around").

Then download CarbonCopyCloner version 3.4. 6 from:
http://www.bombich.com/download.html
(Note: version 3.4.6 is the last free version of CCC)

Put the drive in the dock, connect it, initialize with Disk Utility.

Now use CCC to "dupe" the contents of your internal drive to the docked drive.

When finished, you will have a bootable clone of the internal, with files in POFF (plain ol' finder format). You can even boot the Mac from the docked drive.

Why a "docked drive" instead of another external?
Because if you need -MORE- storage capacity, just pick up another bare drive and put it into the dock. You can swap drives as needed. A VERY useful gadget to have around. And I did mention that they were CHEAP?