[V7/x86 Issues List as at 06 May 2012]

In the install environment, the file /boot/mbr is missing. This is needed
by ptdisk when initializing a hard disk that lacks a partition table. A
workaround -- and the preferred approach anyway -- would be to partition
the disk using some other software before beginning the V7/x86 install.

V7/x86 sometimes seems to work less well on VirtualBox than it does
on actual hardware and other emulators and virtualization products.
In particular, a fresh installation from CD image sometimes fails:
a situation I have so far been unable to reproduce except when using
VirtualBox.  A workaround to the install problem would be to use the
supplied pre-built virtual machine.