installing windows vista

hey guys.. I have a hp 550.. Im having trouble installing windows vista home edition on it.. It has x.p currently.. But when i try to install vista it completes copying the files etc. But the stage where it finalizes the installation its gives me an error stating...
''windows cannot continue installing because windows cannot configure the boot configuration. Installation will be cancelled''
but when I install x.p service pack 3 it works fine..
Is it my cmos or something else? if anyone can help i'll be really grateful.. Thanks soo much