How do I disable fan POST error on T3500

My "front fan" (the one that cools the processor) failed, so I removed it from the assembly and moved the "card cage" fan down to where the front fan was. But now I get an error for the card cage fan. I have a single low-end graphics card with its own fan attached to the card so I don't really need a card cage fan. The memory never gets warm either. I don't see any way to disable the fan in the setup utility (F2). Please help.