Normally that option can be found and edited in the BIOS under configuration>memory overrides tab, but due to the fact that your system is an original equipment manufacturer (OEM) you may want to contact Gateway* so they can confirm if this option can be seen in your BIOS.
You may want to contact them at 800-846-2301
Tried calling, got told my product is not eligible for tech support. I bought it refurbished, maybe that's why.
Now what? I've tried using other tools like CPU Tweaker and SPD Reader, both of which failed.
I tried running HWInfo32, and it reports that my RAM is running at 5-5-5-14 timings. Huzzah!