Failure to boot from HD formatted not by FreBSD

[Yuri]

I wonder what are the limitations of MBR (/boot/boot0)?
I have the OEM-formatted harddrive (160MB), on which I want to add 
FreeBSD into the free space.
I created the FreeBSD partition, set MBR (in 8.0-RC2), but  when it 
displays the boot prompt and I hit some key I only see '#' character 
printed and nothing happens.
When I took MBR from my older FreeBSD HD and placed it on that one, it 
doesn't print '#' characters but also doesn't boot.

When I boot into the healthy system with this new OEM HD attached I also 
see dmesg messages like this:
GEOM: ad4: partition 2 does not start on a track boundary.

What could be wrong, why it doesn't boot?

Yuri


--- partitions in MBR ---
Media sector size is 512
Warning: BIOS sector numbering starts with sector 1
Information from DOS bootblock is:
The data for partition 1 is:
sysid 7 (0x07),(NTFS, OS/2 HPFS, QNX-2 (16 bit) or Advanced UNIX)
    start 2079, size 44039457 (21503 Meg), flag 80 (active)
        beg: cyl 0/ head 33/ sector 1;
        end: cyl 1023/ head 116/ sector 63
The data for partition 2 is:
sysid 15 (0x0f),(Extended DOS (LBA))
    start 220416000, size 61222912 (29894 Meg), flag 0
        beg: cyl 1023/ head 255/ sector 63;
        end: cyl 1023/ head 53/ sector 58
The data for partition 3 is:
sysid 18 (0x12),(Compaq diagnostics)
    start 281638912, size 30942896 (15108 Meg), flag 0
        beg: cyl 1023/ head 255/ sector 63;
        end: cyl 1023/ head 80/ sector 63
The data for partition 4 is:
sysid 165 (0xa5),(FreeBSD/NetBSD/386BSD)
    start 44041536, size 176373792 (86120 Meg), flag 0
        beg: cyl 1023/ head 255/ sector 63;
        end: cyl 1023/ head 55/ sector 63