Downgrade. Hi! i have a problem with my toshiba satellite L40 regarding to its downgrade. i want

Question

Hi! i have a problem with my toshiba satellite L40 regarding to its downgrade. i want to downgrade the OS from vista to xp but saddenly the setup will not continue after this massage came out "press any key to continue" i press space bar and then the display goes only dark..I've wait 10 min. or more but it sames no progress at all.. what should i do with this? Please help me.