The CTRL+ALT+Del is the OS user account password, but the other one, not allowing to boot up from a CD sounds like a BIOS password, not an Operating System Administrator password.
Do you know any of the IT staff that worked at this company? If so, I would ask them. Other than that you will need to reset the BIOS yourself but nothing is guaranteed.
Try http://www.tech-faq.com/reset-bios-password.html and also look through that link for "Resetting a Dell BIOS Password".
Mark
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