here is what i would do:
get active killdisk (http://www.killdisk.com/
make a bootdisc for windows, then copy the files for active killdisk on to it.
change your BIOS setup to boot from floppy.
boot from the floppy, and choose "minimal boot" or "boot to command prompt".
wipe all your data by selecting your hard drive (not the floppy), and tapping f10.
boot ubuntu from Livedisk, and activate its partitioning utility. (I think it uses QTPARTED, just type qtparted in the shell)
in this order, make a FAT32 partition, an EXT3 partition, and a LINUXSWAP partition, of the size you want.
don't install ubuntu. once you partition the drives, abort installation.
boot and install Vista from CD, you should be given a prompt about unknown drive partitions. Tell the computer to continue.
Boot and install Ubuntu from disc, it should come kernalized to install GRUB.
this should be it, but have another computer available to get help on the internet.
good luck! and screw VISTA, get XP.