"Boot device not available" on Dimension 5100

I just recently acquired a Dell Dimension 5100. I was trying to install XP MCE 2005 on it, since that is what originally came on the machine. I put the MCE disk in the drive and power on the system. "Boot device not available". I changed the boot order so the CD drive is first, since I am trying to reinstall XP on it. Same error. I restart it over and over with the same error. The system currently has no OS on it. How can I fix this problem? Thanks!

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