OpenBSD doesn't recognizes FAT partition on virtual disk mapped to phys HDD on MS Virtual PC
disklabel wd1 (virtual disk mapped to phys HDD on MS Virtual PC) just displays one partition - "c".
At the same time i remember, that on VMWare disklabel for virtual disk mapped to phys HDD displays two partitions - "c" and "i" and i've mounted it without problems like that - mount /dev/wd1i /mnt/win (it works without -t vfat parameter!)
p.s. the order of parameters to "mount" differs between linux and openbsd. e.g. - -t parameter MUST precede nodes in BSD.