http://en.community.dell.com/support-forums/servers/f/906/t/19322091
Boot to BIOS (F2) and check for any "unknown" devices - especially SATA ports turned on with nothing attached. Turn the port off if it shows unknown. F1/F2 signals a misconfiguration of some kind and is simply an attention-grabber so as to make you aware of the problem. Hitting F1 should still boot the OS.
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