MacOS – install Snow Leopard over a network

Two things - if you don't know the basics of a unix shell syntax (having a space in the right place matters, punctuation like / matters) don't do step 2 unless you can afford to re-install everything again - the rm command is unforgiving - delete the wrong file or directory with rm -rf and the mac won't boot. You can be more secure by using the srm command instead of rm and it will slowly shred the files - I use srm -sz -rf instead of rm -rf below to shred once and then zero out (which ends up being two passes and then a delete - plenty secure for my needs and not as slow as the default 35 pass overwrite before the delete)

1. Do make sure the person buying the machine knows what they are getting recovery disks for. It's really nice to make a test account to run all the updates rather than hand them the Snow Leopard disk.

2. Set up your Snow Leopard Mac to add one admin account named test with no password and delete any other accounts using the test account. Reboot into single user mode by holding command + s and type these exactly:

    /sbin/mount -uw /
    cd /var/db
    srm .AppleSetupDone
    cd dslocal/nodes/Default/users
    srm test.plist
    cd /Users
    rm -rf test
    halt

You can now boot the mac to see the setup welcome movie plays and quit the assistant a few steps in using command + q when it starts asking name questions and it will shut down with no account created but all the applications preserved. It will remember your wifi settings, so delete those before starting step 2 or use ethernet/a safe public wifi to run updates if you're worried about that sort of thing.

• I have a copy of Leopard that came with the MacBook. However it fails checksums.

You can try to repair the disc using this method. Never done it but the author claims he has, and it worked for him. Your mileage may vary.

• I have an upgrade copy of Snow Leopard on DVD. (Unsurprisingly?) the MacBook won't install from it.

You seem to have bad luck with physical media. From this source (and Diago below), the Snow Leopard upgrade disc contains a full installer, allowing the installation even over a system without any OS whatsoever. If it fails to boot, it could likely be damaged.

• I have a full copy of Snow Leopard for Mac Mini - I tried to install and it says it doesn't work on MacBooks.

That is also correct. Minis (like many of the machines Apple manufacturers) come with their own specific versions of OS X. The Mac minis, like the MacBook Airs ship with special versions that differ from the ones you purchase through other channels. Therefore, you cannot use an installation disc from a MacBook Pro on a MacBook or iMac.

• I have a new MacBook Air with Lion preinstalled.

Apple machines that ship with Lion cannot be transferred to other devices. If you purchases Lion through the Mac App Store, you could install it on any Mac (except those that ship with them of course).

In all honesty, the best advice I could give you is to book an appointment at one of your local Apple Stores and speak to a Genius. Tell them your situation (bring in the machine and the Tiger installation disc). They'll either give you a Snow Leopard installation for free or boost you up to Lion. I'm not sure if they will give you a free USB Stick, but they'll do something for you. I guarantee that.