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Sorry dude, this is a total scam. You really have to ignore these on craigslist as you will get at least one on every listing you make. Always meet in person, preferably in a public place. Ignore ALL offers that involve shipping. His willingness to overpay (sorry, your PowerMac isn't even worth $1400) is absurdly obvious.
 
Stop!!! This Is A Scam!!!

STOP!!! THIS IS A SCAM!!!

Don't do it man!!!! Seriously, I've seen these before, it's a scam. You end up posting the item before the cash is in your account, and then guess what happens? The cash "mysteriously" doesn't show up in your account, and you've just lost your computer. They try really hard to convince you that the payment is "pending" or "approved" by some phony website, but until the money is actually in your bank account, don't part with a thing. If you insist on this, then I guarantee you won't hear from these guys again, which will prove it was a scam.
 
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