Hi,
You need to do manual partitioning to achieve your goal. I assume you are using an external hard drive (USB). You need to keep in mind that windows only scan/use the first partition on an external drive.
Nevertheless, it is possible to do what you want by installing groovyarcade first, then doing some repartitioning (Linux knowledge required). Let's assume you used the gasetup script for the installation. You should have GABoot and GARoot, swap and roms partitions. First, backup the roms partitions layout somewhere (use rsync is possible). using another distro (like live CD Ubuntu) use the (g)parted utility and do the following.
- Delete roms partition
- Move all partition at end of the dist to free space at the beginning of the dist
- Create a new first ntfs partition at the beginning
- restart PC with groovyarcade CD
- rewrite the syslinux/grub mbr (cmd line can be taken from gasetup)
- mount the GARoot and edit the fstab file to map the roms partition to your new ntfs partition
Ta da. Reboot and it is done. If you plug the disk on a windows computer, it will show you your roms partition.
I know, it is not start forward. Hope you will succeed ;-)