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Sounds like the Apple guy hooked up a drive and used Disk Utility on the external drive after booting to it ("when he held alt and boom").
 
Here's why I'm asking: Threads like this one show up in query responses (Google and others) when folks are trying to fix problems on their own (much as you did). Final posts like yours above don't close the loop. Like many, you received some pretty good help from complete strangers so please, finish your part and tell them what the fix is.

It's also one of the reasons I came to MacRumors in the first place it to learn. So it's nice to know how to fix problem I don't know anything about.
 
If anyone else should happen to find this post via Google, I just discovered that my MBP, which shipped with OSX 10.6.3 absolutely will not boot from a retail Snow Leopard disc. I eventually found the gray-labelled install disc that came with the laptop, and it booted from that without any problem.

Very annoying if you just need to get into Disk Utility without running from the system volume. :mad:

Point being that for whatever reason one simply cannot boot from a retail SL disc on a system that shipped with SL.
 
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