Q: White screen with a folder with question mark?

If your Mac came with a disk and wasn't upgraded to use Apple's Internet Recovery system(this isn't possible on all Mac models), you need to use a disk to perform the initial OS installation. In this case, it's generally best to use a Snow Leopard one.

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If you're accessing the Internet Recovery system(Option, Command, and R), it may be slow; wait for a while.

If you're trying to access a NetBoot server(N), it'll only work if there's a machine running Mac OS X Server on your network.

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How are you attempting to boot the computer - using Internet Recovery?