wiped disk - no longer bootable

[Volker Wysk]

Hi

The problems pile up. I've wiped the first megabyte of both devices  
(HDD and SSD), because I got a message on boot which sayed that the  
disk with a specific ID can't be found. Using "dd if=/dev/zero  
of=/dev/sda ...". Then installed Ubuntu again, which appeared to  
succeed. But when booting now, it says that there is no bootable medium.

So I have wiped something which I shouldn't. How do I restore that? It  
doesn't seem to be something which fdisk does.

:-(


Bye
Volker