Very easy.
Method A:
After the installation of FreeBSD ( one harddisc diffrent paricular mode).
1. Copy the /boot/boot1 (in Install Disc) to C:\
2. Edit c:\boot.ini, add follow line in [operating systems] section:
C:\boot1="FreeBSD"
Done.
Method B:
After the installation of FreeBSD ( any mode).
1. boot in to freebsd
2. #dd if=/dev/da0s3 /of=/bsdboot bs=512 count=1
3. copy the file bsdboot to your windows C:\
4. edit C:\boot.ini add C:\boot1="FreeBSD" in [operating systems] section.
Method C:
After the installation of FreeBSD ( any mode).
1. Use WinHEX to get the first 512 byte from your BSD installed partition.
2. Save it to a file named bsdboot
3. like Method B