Try the DEL key..........................

Try
www-307.ibm.com/.../document.do

I tried del and alt delete and the IBM screen
flashes on for a moment and then opens My present program which is
ubuntu 8.04 but it runs on a different kernal for Emc 2. I also
would like to boot from a cd or dvd but am having no luck. I bought the
computer on line but the model number has been scratched off so I don't
know what it is other than IBM Think Center. Anybody have any ideas??

You could always try setting the BIOS back to defaults via the motherboard
jumper. At default settings, the screen that provides the 'enter BIOS' prompt
should show up again. Unless, of course, IBM did something really obnoxious
with the BIOS.

I did a google search and found this site which may or may not
help. But it couldn't hurt to look and try.

michaelstevenstech.com/bios_manufacturer.htm

did you try to press F1 after the POST and before the Boot ?

I had brought the old IBM in the house to use and put my
HP out in the shed to temporarily run CNC with EMC2 . Today I bought an
old computer for that purpose so I will set the IBM on the shelf as a
spare. I would still like to get this one to start on a cd but will set
aside a few days and then get back to it. I think I did what you
suggested but I will try again to be sure.

Have you tried the DEL key?..............