Other options: Provided the OpenBSD disk is hardware compatible with the Windows PC (Not an AMD64 OpenBSD disk in an i386 Windows PC) you should be able boot the OpenBSD disk directly.
Then you could use
tar(1) to archive/compress the files on the OpenBSD disk and then write them to a CD or USB drive.
Or you can edit /etc/inetd.conf to allow ftp transfers and
Code:
/etc/rc.d/inetd restart
which turns the machine running the OpenBSD disk into an ftp server. Then ftp into the new server and copy the needed files.