Optiplex will not boot

My Optiplex SX260 is causing me problems.

It was currently running with an english version XP Professional. I have now tried to complete uninstall this version bu using a Clean Wipe program. Then tried to install a Danish version of Windows XP Professional. (Would not boot on a windows 7, or windows 8.1, why?) Now I am facing this problem: Could not finish this installation with the danish version, as the installation asking for the SP1 disk, which I do not have.

Further, it is not possible to boot from the Cd-rom drive anymore. I get this message again and again: Strike F1 to retry boot, F2 for set up utility. 

How can I get the Optiplex to boot from the CD-Rom drive again? I am lost. Any advice appreciated. Thanks.