tl;dr my computer is doing stupid **** it didn't 3 months ago, wont boot from external hdd or dvd with os x snow leopard installer Hello all After getting fed up with OS X Lion on my 2010 MacBook Pro I finally decided to downgrade back to Snow Leopard, except it's like my laptop doesn't really want me to. I downloaded a vanilla dmg of 10.6.3 just like the one on my now-unreadable original install disc and made an install partition on an external hard drive and burned it to a dvd. Both are recognized in the boot select menu, but the booting stalls when loading the drivers for the system. In the case of the external disk, this seems to be because the drive loses power. The activity light goes off and the drive spins down in the first second of booting. The disc spins at full revolutions longer and does not stop immediately, but the booting stalls in the same place as with the external drive. It does spin down, but I can't distinguish whether it spins at 1x speed or is still. Either way, this is not the behavior I recall from installing Lion off of my external hard drive three months ago, or from clean installing snow leopard multiple times over the last year off of the vanilla disks. Any insight and help would be appreciated, thank you in advance.