Vista - Surround sound

I am having problems enabling surround sound on my hp laptop, usually i can
take it college and plug two sets of head phones in and the same audio comes
out of both.

But when i get home i want to enable surround sound, which requires me to
plug my speakers into both audio jack, when i go to devices and try to enable
surround sound the option in unselectable.

Is there anyway to get past this, and maintain both modes of use?
I have updated the drivers to the newest ones.

Any help would be great