My system specs:
XP Home
Q6600
4GB 800MHz
MSI P6N Diamond
1 x 250GB HDD
1 x 750GB HDD
2 x 1TB HDD
Geforce 260
Whenever I play in the nubula missions I'm suddenly afflicted with horrendous FPS slow down which makes it impossible to dogfight other than just spamming missiles. That bombing mission was next to impossible but I still managed it. Anyone know any fixes?
Secondly, is there anyway to un-invert the mouse X-axis movement? It's really... awkwad.

I'd recommend trying FS2Open. With those specs, you can enable awesome graphical updates and I bet it would also solve the slowdown issue. Manual installation can be done as explained at http://www.hard-light.net/forums/index.php?topic=47640.0 . The FSO Installer ( http://www.fsoinstaller.com/ ) should accomplish the same steps automatically, if you wish to give it a shot.
I can't remember exactly where, but somewhere in the in-game settings there is a switch for toggling this option on/off.

Options -> Control Config -> Ship then click on "Turn (Yaw) Axis" and click on the Invert option.

Awesome, thanks dudes. Being able to actually go into a dog fight and have some bit of marksmanship in pumping those nasty Shivans has made the game all the more fun.
=3