Spinrite 6

I have a copy of spinrite 6, i brought it in to work today to help my boss recover his external HD. We tried to boot from the cd on a Dell optiplex 745. The Press any key to boot from Cd came up, then the “pre-spinrite info” was displayed and said Initdisk at the bottom. It didnt make it to the spinrite user interface it just froze there. Is there any known reason for this issue? I brought the disk back home and tried it and it worked on the first try!

Any help would be great
Thank you!