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I can’t get AHCI mode to work on a Dell Optiplex 755. I’ve installed the drivers, but when rebooted in „RAID Autodetect/AHCI” mode, the system hangs. No Windows logo, no BSOD, nothing. Only a blinking cursor in the upper left corner. The system boots from CD in AHCI mode just fine.

UPDATE: I confirmed it to be a driver problem. When doing a clean install, the system boots fine. Can anyone tell me how to install the AHCI drivers after installing Windows? See solution below.

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migrated from Jan 6 '12 at 23:13

This question came from our site for system and network administrators.

Windows will not load the AHCI driver upon boot if the drive controller was not in AHCI mode at the time of OS installation. You need to set the machine to AHCI mode PRIOR to the installation of Windows.

With that said, there is a registry hack that can be performed to enable the AHCI driver:

Prior to switching the system to AHCI, locate one of the following registry and set its value to "0":




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I have done that already. Let me repeat: the computer hangs before even getting to load Windows. – kinokijuf Jan 6 '12 at 21:40
What version of Windows are you using? – newmanth Jan 6 '12 at 21:43
XP (13 more to go...) – kinokijuf Jan 6 '12 at 21:45
We have 755s running XP too. I believe they require that the Intel 82801 FBM SATA AHCI Controller driver be installed for AHCI to work properly. Look for R173412.exe on the Dell Support website. I can't say for certain that will fix the issue, but I know we needed to deploy this prior to XP install on any of our AHCI-configured 755s. – newmanth Jan 6 '12 at 21:49
XP is a lot harder to switch to AHCI after install, start over, reinstall XP with AHCI set in the bios...The MS KB922976 you pointed to is for W7 and will not work for XP. – Moab Jan 7 '12 at 0:51

Are you running the latest bios available from Dell for that 755? I once had an external USB CD drive that would cause a similar symptom on a Dell until I actually downgraded the BIOS to an earlier version (was running the latest version).

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Not 100% sure that this is related (since the description in the article is not 100% clear) but there seems to be an indication that faulty DVD firmware may lead to hanging issues,

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What in the description is not clear? – kinokijuf Jan 6 '12 at 21:44
Also, it hangs before even getting to the boot screen. – kinokijuf Jan 6 '12 at 21:46
This computer has a different DVD drive. – kinokijuf Jan 6 '12 at 21:50
up vote 0 down vote accepted

Somehow the ICH9 southbridge didn’t like my partition setup. I shrank and then enlarged the partition again using a Paragon boot CD and then it started working.

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