go to your systems manufacture.
I looked online apparently your XPS has
Dell P965 BTX motherboard
it could be wrong but find the BIOS for this GOOGLE is your friend.
download to flash drive
keep in mind from another computer
then go to your XPS start it up
plug in the flashdrive into the XPS
Hit F10 i do believe that is the boot menu option
find the flashdrive from the boot menu and hit enter. it should boot from that flash drive.
and wah laaa updated BIOS