How to enable ACPI to edit settings for computer fans

I recently bought a new dell laptop gx200 and switched from the old one which was also a dell. The old laptop use to turn off his fans when I put it in sleep mode while the new one will not do this. To find out why I did some research on the internet and it says that I need to enable my ACPI and set it to S3. I tried checking the BIOS for the option but there is nothing there remotely related to fans not even in the power management section. Any idea how I can enable this.
