Hello all, I have a 15 inch Intel MBP 4,1 (early 2008), 2.5 ghz, 4G RAM (upgraded from 2) with at 250GB hard drive running 10.6.8. Can I reformat my MBP's hard drive and then reinstall OS X 10.6 without the use of my built-in DVD drive and use an external HD with the OS X 10.6 dmg on it? My DVD drive hasn't been working for about a year but I hardly use it so never bothered to get it fixed/buy a new one. I have 10.6 (not the version my MBP shipped with) on an external USB HD (GUID) that I used as a bootable disk to upgrade from 10.5 and I wanted to know if you could still do this after reformatting the MBP's HD ie. if I reformat it, will I still be able to hold down 'option' once booting up with my external plugged in and it will show up like it did before? This is my first time reformatting my HD, I have read many articles but they all suggest that you have your instillation disk and use this during the process but since my DVD drive doesn't work it's not an option for me. I tried calling Apple Support but they just said that what I want to do isn't suggested but "theoretically should work" so seeking some confirmation here. My fear of course being that I reformat then find my external bootable drive doesn't show up. And yes, I have Time Machine backups and manual backups of all the important stuff. My MPB has been acting quite odd and slow and this has increased over the last 9-6 months. To be more specific, taking forever to load the desktop, opening applications, applications freezing and having to hard shutdown, etc. I have tried multiple 'fixes' to speed it up: reset VRAM/PRAM, reinstalling OS X and using Time Machine to restore, defrag, ONYX etc... Upgrading to 10.6 from 10.5 seemed to speed things up but after some recent issues I decided to just backup and reformat and start fresh. Many thanks in advance for your time and any help.