goto DOS and put the ME cd in the cd rom, then type: X:\setup (x being the cd rom drive). Then during the installation, install it to another partition different than the xp one...make sure that the partition u are instaling it to is FAT32 or it wont work.
6 gigs is plenty more than you need for an OS ..i have my xp partition at 4 and thats enuff for me. Besides xp is a hell of a lot bigger than ME. You should really consider going with 98SE instead, ME blows