yes you have probably let the mbr installing on ur hdrive
you should try with a windows diskette or usb boot disk to go to "recovery console" and type fixmbr.. that willl work
next time be sure to write ur mbr to the usbkey(select the right part,something like "sdb1_removable" form me
hope helps
ps you can just boot BT from cd and go into your usbkey and run /boot/bootinst.sh RUN IT FROM UR USBKEY.... will install mbr on usb....


