On a computer that runs Windows Vista or Windows Server 2008, a Peripheral Component Interconnect (PCI) Express bus may run in PCI compatibility mode instead of in PCI native mode after the PCI root bus restarts. For example, the PCI root bus restarts when you disable and re-enable the root bus in Device Manager. Therefore, all PCI Express-related functionality, such as Windows Hardware Error Architecture (WHEA) and power management, is turned off.

Consider the following scenario:

• You have a computer that is running Windows Server 2008 or Windows Vista Service Pack 1.
• The computer has a Peripheral Component Interconnect (PCI) Express interface.
• You have at least one PCI Express card that does not fully support Active State Power Management (ASPM) inserted.
• You restart the computer.

In this scenario, an internal error may occur during restart. For example, a CPU IERR error may occur. Additionally, the system may stop responding.

This problem occurs approximately one time in every 500 restarts. Therefore, you usually experience this issue only when you are running restart tests. However, the risk of this problem occurring increases significantly if the following conditions are true:

• You apply hotfix 952681 on the computer.
• You insert PCI Express cards that do not fully support ASPM into all available PCI Express slots.

Consider the following scenario:

• You have a Peripheral Component Interconnect (PCI) Express interface that supports the “hot plugging” feature on a Windows Server 2008-based computer or on a Windows Vista-based computer.
• You connect a device to the root port of the PCI Express interface.
• You use the “hot plugging” feature to add or to remove a PCI Express device on the computer.

In this scenario, the Windows Server 2008-based computer or the Windows Vista-based computer may be restarted unexpectedly. Additionally, you receive the following error message:

0×00000124

Note: When you restart a Windows Server 2008-based computer or a Windows Vista-based computer, the issue may also occur if a PCI device is connected to the root port of the PCI-Express bus on the computer.

When you connect a removable PCI Express device, such as an eSATA ExpressCard device, to a Windows Vista-based computer, the device does not appear in Safely Remove Hardware dialog box. Therefore, you cannot safely remove the device.