I have 3x OptiPlex GX620 machines that I need to format and re-install with Windows 7.

When I get to the step where I "Press any key to boot from CD or DvD" then all 3 machines starts to load all the windows files but as soon as the machines gets to the screen where it says "Starting Windows" then it just halts/stops and wont go any further.

My company does not use the Windows 7 CD/DvD that can be aquired from DELL, but we have them directly from MICROSOFT. Is there something with the MBR/BIOS that blocks the CD/DvD when its not an OS configured/delivered by DELL?

What can I do my self to fix this issue so I can get on with formatting and install the machines with Windows 7.

Thanks.