Hi, Steve:
Normally you need to tap the ESC key at the beginning of the HP welcome screen to access the various menus such as BIOS or Boot Options.
If that doesn't work, I recommend you post your question on the HP Business Support Forum -- Z Workstations section.
http://h30499.www3.hp.com/t5/Workstations-z-series-xw-series/bd-p/bsc-272#.UryQ0el3u9I
