Gateway SX2800-07 Memory upgrade not working, wondering if BIOS may need updated?

Hello, My father has a 12 year old Gateway SX2800-07 that runs great for what he uses it for. The fan in his PS went out, so I replaced it for him, and while doing so, I saw he has two DIMM slots open.

Given the limited spec info I could find online and the labels on the existing DIMMs, I ordered a set of two more 4GB DIMMs. As soon as I power it on, the system gives an ongoing error sounding tone. I presume it doesn't like the new DIMMs, but as far as I can tell they're well within spec. I've looked for a BIOS update that may be available, but I'm not finding that either.

Existing BIOS: AMI P01-B1 11/12/2009

I bought DDR3-1333 DIMMs, but I noticed the label on the existing DIMMs are GDDR3. Do I have to have GDDR? The specs I found online only refer to DDR.