help with my dv6-3143us

I just bought a dv6-3143us and I have some issues:

1. When playing an old game, Medieval 2 Total War, it stutters at some points even though the details are at medium and low. It won't let me download and install the latest drivers for the Mobility HD 5650 and says that my hardware or software does not support the drivers, as it seems that only HP drivers are accepted. This means I am stuck with whatever drivers HP decides to update to, which always lag behind ATI. I have updated the bios and everything else to the latest HP-enabled drivers. HP bloatware was manually uninstalled, I ran a defrag, and I make sure that background processes are to a minimum, though it shouldn't matter because the game only uses 1 core. So what's the problem?

2. The battery life sucks. I would like a 12-cell battery, but it seems it will have to be aftermarket (HP only makes 9-cell for the dv6-3000 series). I have no idea which battery will work with this laptop, or which aftermarket battery manufacturer is the best. Will a different model HP battery work with this laptop? What aftermarket batteries will work with it? I am lost in the sauce and need some expert help.

Here are the specs:

core i3-370m @ normal speed (2.4 ghz)
ATI Mobility Radeon HD 5650 @ normal speed
4GB Ram
500GB 5400 HDD
Windows 7 premium 64 bit

Any help is appreciated. Thanks.