How to disable IRQ sharing for 16-Bit PC cards that do not support ISA-to-PCI routed interrupts

The R2 PC Card does not start, and you see the following error message in Device Manager:

This behavior occurs because some R2 PC Cards do not support interrupt request (IRQ) resource sharing. In Windows XP or in Windows Vista, 16-bit PC Card (PCMCIA) PCI readers can use R2 PC Cards (the 16-bit ISA type) without requiring an ISA runner paddle to obtain ISA interrupts.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

To resolve this behavior, disable the ISA-to-PCI routing feature to allow these PC Cards to function in laptop computers:

1. Start Registry Editor (Regedit.exe).
2. Locate and click to select the following key in the registry:
   HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\PCMCIA\Parameters
3. On the Edit menu, click New, click DWORD Value, type DisableIsaToPciRouting in the NewValue box, and then press ENTER.
4. Click to select DisableIsaToPciRouting, click Edit, and then click Modify.
5. In the Value data box, type 1, and then click OK.
6. Quit Registry Editor.

This procedure disables PCI routing for 16-bit PC Cards. With this feature, you can successfully install 16-bit PC Cards on computers that are low on ISA interrupts by using a shared-PCI interrupt.

Note: If you disable this feature, the device could potentially display an error code 12 (not enough free resources) in Device Manager if there is not a suitable free interrupt for the card to use. You may have to disable an unused device or port to make an IRQ available for the card.