The standard default voltage for DDR2 RAM is 1.8 volts. Generally, running the RAM at 2.2 volts is safe.
But motherboards are different. My Gigabyte motherboards using DDR2 RAM can supply more than 2.4 volts. You need to go into the BIOS and check the available voltage range. When you do, you have 2 possibilities: you can either adjust the RAM voltage or you can't.
If you can adjust the RAM voltage, you will see one of two ways.
You will see either a list of absolute values - "1.80, 1.90, 2.00, 2.10, 2.20, 2.30 volts", etc - like my eVGA board or
a list of increment values - "0.00, +0.10, +0.20", etc - like the Gigabyte motherboards. These are referenced to 1.80 volts. To run your RAM at 2.2 volts, you would select the "+0.40 volt" value.
One of the reasons that you would overvolt RAM is to run it at a higher than rated speed or to increase stability if you have mixed RAM. Some motherboards have problems running 4 sticks. Overvolting can help here as well.
If the CPU has an integrated memory controller, things are a little different. Running the RAM at a higher than stock value can damage the CPU.
The datasheets for DDR2 chips specify an absolute maximum of 2.3V, meaning they can be run almost indefinitely, or at several years, at that voltage without harm, but I don't know if the maximum air temperature can be as hot then.
That motherboard's BIOS has setup options for selecting a memory voltage higher than 1.8V, but there is no reason to do that unless the memory is of inferior quality. I don't know if the BIOS will read the SPD to set the voltage automatically.