Windows 7: How to keep my surround sound headphones configured to 7.1 not 5.1?

I just got some surround sound headphones. When I restart my computer after having set my sound configuration for the headphones to 7.1 (supported by these headphones) the sound configuration will be at 5.1. I don't know what is causing it to keep going to 5.1. Any ideas on what I can do to fix this so my sound stays at 7.1?

When the set up is at 7.1 the two rear speakers are enabled. This might seem small but I play battlefield 3 and being able to better hear enemies who are behind me will help me play better and this is one of the reasons I got the headphones so I definitely prefer these two speakers to work.

There`s no such thing as 7.1 yet, the others channels are just made up from the source audio. Headphones are only 2 channel. No matter what you were told.
Everything is downmixed to 2 channels.

Are you sure? When I did the configuration where you can click the individual speakers and listen to which speaker it activated in the headphones, the two additional speakers brought on by 7.1 (the rear ones) sounded distinct when I clicked on them. For this reason I do believe that a 7.1 configuration benefits my headphones.

So considering what I said above, would you say that 5.1 enables those two rear channel speakers in the headphones? (this would mean on a 5.1 setup there would be front center, front right, front left, side left, side right, subwoofer, and rear left and rear right)

5.1 is left, center, right, left rear, right rear, and subwoofer.
7.1 adds left and right sides to the above.

What headset do you have?

I have plantronics gamecom 780.

I thought the rear speakers were added by 7.1 because when I toggle between 7.1 and 5.1 in the sound config the rear speakers are the ones that disappear with 5.1.

First off those are not 7.1 headphones. What they are is stereo (only one speaker in each cup), and the 7.1 is done using the Dolbly surround/headphone setting in the heasdsets control panel,

Plantronics Gamecom 780 Review