Yes, you can. But I wouldn't recommend it, because since your MoBo only allows a max speed through a DIMM lane of 1,330 MHz (1.330 GHz).
Like the guy above said, it is your best bet to remove the 2 GB stick/module you have now and get a 4 to 8 GB module. If you want to keep your motherboard, just save a bit and buy a regular 1330 MHz stick or two instead of a 1600 MHz module. I would recommend going 2x4GB for 8 GB total, or 2x2GB if you are going to 4 GB. If you have a 32-bit OS, you can only use 4 GB of it. Think of it like this:
32-bit OS = Able to use 4 GB or under of available RAM (Random Access Memory).
64-bit OS = Able to use up to 80 BILLION GB RAM, if that were even possible.
2x4GB (dual channel, total of 8 GB) > 1x8GB (single channel, total of 8 GB)
2x2GB (dual channel, total of 4 GB) > 1x4GB (single channel, total of 4 GB)