GRUB/bootup problem

Hello and greetings to all I had the "studio64" release on my GIGABYTE AMD939 computer, and it was working fine until I installed a version of debian5_isolinux 3.71_peter_anvin onto a usb-key hd and REMOVED THE USB-KEY. now I get : boot from cd DISK BOOT FAILURE, INSERT SYSTEM DISK AND PRESS ENTER Can anyone help, please? My idea was to make a "portable" copy of debian that I could use anywhere.but now it seems that my computer "needs" this usb key. I have tried to force the bios to use only hd boot (same problem) -and reinstall grub from the linux5 cd in rescue mode (same problem) ciao for now