[ubuntu] Copy bootable CF and convert to vdi

Hi

I have been struggling with this all night.
if I use
dd if=/dev/sda1 of=/home/wizball/Desktop/access1/convert/cf.image

to copy the CF it just copies the files it seems and does nto make a boot able vdi afterwards.

If I use
dd if=/dev/sda of=/home/wizball/Desktop/access1/convert/cf-card.img

after mounting the cf to sda1 then it copies the cf and see,s to go on to the hard drive that is also mounted there.

I have looked around the Internet for solution but cannot find one.

I have managed to convert the image that is produced using
VBoxManage convertdd cf.image cf.vdi --format VDI

but it will not boot.

I am connecting the CF card to the computer via usb.

many thanks in advance
Peter