Vista home premium 32 bit won’t boot. normal steps not work, help?

I have a gateway with vista home premium 32 bit. no oem cd for OS. I have a boot disk downloaded from MS. When installing update 3 of 3, computer hung and would not complete update. I had to turn off the computer. now it won’t boot. It says no bootable device, insert disk etc. i have used the repair disk with MS Support to no avail. I have tried rebuilding the bcd to no avail. Gateway can’t supply me with recovery disks as the machine is over 3years old. Can someone point me in the right direction for next steps?