Booting from DOS?

I have just installed 5.3

I have a 100mb dos partition, 70mb swap  and the rest of the 2gb hard 
drive as one bsd slice

The BSD slice is all one filesystem "/"

When my system boots it gives:

F1 . . . DOS
F2 . . . FreeBSD

Default F?

When I press F1 I get DOS

When I press F2 the boot prompt repeats.

I have tried to BOOTINST again. The same thing remains.

What's wrong?

Is there a way to boot BSD from DOS?

Thanks for your help.