I'm fiddling about trying to get a multiboot system (win7, ubuntu, lion) on one drive working with grub 2, but was wondering what the msdos part meant on my system. I don't see it like that on any of the examples online.
It is used to distinguish between MBR-style partitions and GPT-style partitions.
For "old" MBR partitions, the prefix is
Note that partitions are numbered starting from 1 in Grub2, while they were numbered starting from 0 in previous versions.
See the Arch Grub2 wiki entry for more on this.