Computer won't boot past HP screen

ok so i was trying to add an additional hd to my parents computer, something i have done several times before, but when i went to power on the computer it just stays on the HP screen, it won't let me into safe mode or anything just stays on the HP screen. so i unhooked the hd and put everything back to how it was and still isn't loading, i also unhooked everything except the keyboard, monitor and mouse and still nothing. i don't have recovery disks for this cause everything is on the computer. so any help would be appreciated because my parents don't know yet and i would like to live to see tomorrow!!! i am using a HP 1203w

 

ok well apparently my computer is possessed cause it seams to work ok now?!