Upgrade to Mountain Lion

I have bitten the bullet and bought a used MacBook, it is running OS X Snow Leopard, the same as on my father in Law’s iMac. He now wants to upgrade to Mountain Lion but is put off by adverse comments about Mountain Lion and would like me to install it first, on my machine, as a trial. I have been having all sorts of speed and drop-out problems with my broadband connection and am considering downloading Mountain Lion on his computer. I have read the article on ‘re-downloading OS X’ How to Re-Download OS X Mountain Lion Installer from the Mac App Store
but am still not clear if I can do what I plan. Can someone answer these queries please?
1/ If I download Mountain Lion to my father in law’s computer do I then HAVE to install it there and then as part of the process? He is not happy with this.
2/ If after downloading and ‘saving’ Mountain Lion on his machine can I then install it on my MacBook by copying the saved file and transferring it? Or do I do the re-download as suggested in the osxdaily link?

I believe if you have a firewire cable you can join the 2 togethter and his will see yours as an external drive . when you run the Mountain lion installer it will ask where to install the osx to. Then you just select your machine.

Even better idea is to make a bMountain Lion ootable USB thumb drive prior to running the Installer, Make sure you have a backup copy of your current operating system.


How to create an OS X 10.8 Mountain Lion install drive | MacFixIt - CNET Reviews

" bMountain Lion ootable" = bootable Mountain Lion

Only for those who don't see the obvious...

Thank you all for your help. My father in law gets a bit tetchy if I 'mess about' with his computer too much. He does a lot of work with PhotoShop and hates the thought of loosing anything so I would like to keep things simple and pursue the path I outlined at the beginning of this post - if I get the right answers to the questions I've posed.
The Firewire sounds promising though!

Just realize - if you install ML onto your machine from "his" Apple ID without purchasing it your self - you will require his Apple ID in order to apply any updates to the OS.

All he really has to do is clone his current drive using SuperDuper! or CCC - boot to the clone and make sure everything is there and it works - then install ML - try it for a week - don't like it - boot back to the clone and reclone it back to the internal.

Or install ML onto the clone - that way he has his main drive untouched and can boot to the ML drive and test drive it.

Also realize that by upgrading from Snow Leopard to Mountain Lion…older PPC apps (old programs before Intel Mac's)) will no longer be compatible…and some "Intel-based" apps that were compatible with Snow Leopard…may not be compatible with Mountain Lion.

So do your "homework" before doing the upgrade!

- Nick