Changed IDE to AHCI, now won't boot at all.

Installed SSD to SATA port 5 2 weeks ago. SSD was set as boot drive, via F12 selection, on first boot after install. Computer worked fine. Today, changed bios IDE selection to AHCI, looking for boot speed increase. Now won't boot, or do anything. Fans run, DVD drives open & close. Monitor screen is completely black.Nothing else happens. Rescue disk use won't work in optical drives as boot hasn't started, at all.

I connected SSD to each of 6 SATA ports with no success.

I wonder if the SSD was really booting the machine. All boot files, etc are still on original boot drive. Again, SSD was selected as boot drive.

How do I get this beast back to working order?

Change back to IDE, do this registry tweak, THEN change to ACHI:
Improve SATA hard disk performance (Convert from IDE to AHCI)

Thanks for the quick reply. I think you are spot on, but The computer doesn't begin POST since the change to ACHI. It doesn't boot, nor start, but there is power to the MOBO. Thus, I cannot get to the BIOS, much less the registry.

Again, thanks for the quick, spot on reply.

If it doesn't POST then the problem has nothing to do with Windows yet. If you can't even get into BIOS to change it back, and you didn't dislodge any cables when moving the SSD one around, then what I would do is to try to reset the BIOS to default, by whatever means your mobo instructions suggest. Or power down, pull all power, and lastly the CMOS battery, leaving it out for a few minutes before re-inserting. Some boards have jumpers or pushbuttons to make this easier.

Thank you maxseven! It all went well. I did the remove power/battery and the BIOS went to the default and all is well.

Glad it's working for you again!

Thanks for the response and the clearly presented registry fix.