Tosh A100 will not boot with new HDD fitted.

Hi,

I have a Toshiba A100 (part number PSAAKC-VA104C) and decided to replace the 80Gb drive that came with it. I bought a Seagate Momentus ST9750420AS - 750 GB - SATA-3, but despite all I have been told about SATA backwards compatibility the laptop refuses to boot with the Seagate installed - even from DVD. It will not even respond to the <F2> Bios request.

I had fitted the Seagate into a USB caddy and used Clonzilla Live to clone the existing drive partitions to it - including the MBR. I fitted the new drive and tried to boot into a Win 7 installation CD in order to use System Repair to make sure the boot record was correct. However, the machine steadfastly refused to boot or to accept the <F2> keypress. The message appears to 'Press <F2> for setup or <F12> to interrupt the boot process', but little progress bar that moves along the bottom of the screen goes so far then freezes. If I press <F2> during startup, the message "Please wait . . " appears but again the progress bar moves so fat then stops.

The new Seagate drive is perfectly readable when in the USB caddy, but obviously not from within a Windows environment started from the original drive because as the new drive had the same signature as the existing drive it was automatically offlined. And the laptop still works faultlessly with the original drive re-fitted.

It will boot from USB or DVD with no hard drive fitted but with the Seagate fitted it the boot process just hangs. I have wiped the new drive of all partitions and held down <F2> when pressing the power switch. I get the splash screen and the "Please wait . . " message bottom left but that's it. The progress bar moves a bit, then stops, the disk access LED is "ON" solidly and the USB access LED is also "ON" solidly but nothing after that. In the caddy it is fine, connected to the SATA port the laptop just freezes up.

Could there be a BIOS fault that could cause this? Or have I just lucked out and bought an incompatible drive?