Dude... i know how u feel.. its frustrating isn't it..
but u can do a simple trick in order to fix this...
i assume taht u have the old graphics driver which u used on your previous win xp.. just open the properties on the driver installer and set compatibility to win xp sp 3.. then install the driver..
let it roll, and u will get an error message.. ignore it and restart your pc.. then check ur vram..
like magic, it shows 256mb.. now u can play PES 2010 on highest setting.. but i recomend playing it on medium, because it will lag a bit on high..