Ok this is a wrong to have to say not Ubuntu again. Double check what version of Nvidia drivers you have. Ubuntu has a really bad habit of dishing up old versions of Nvidia drivers leading to problems. Disable desktop effects and remove pulseaudio from your system most likely the cause of all the steam and Half-life speed problems. 2d rendered games have issues with wine normally. Hopefully in 2009 lot of issues will be able to got on top of. None of your desktop interface under Linux has hardware 2d acceleration yet that will be in the next x.org X11 server. Ie part of the problem is technical limitations.
