HL2 runs fine without SP2...
I understand it's a laptop you have there? If so, video card might be the problem.
Right-click desktop, go to Properties, then the Advanced tab. Bottom left, there will be a resolution slider, and above it will say some monitor name on video card name, we need those. For instance, it can look like "Samsung 957 MB SyncMaster Magic on GeForce FX 5700".
I understand it's a laptop you have there? If so, video card might be the problem.
Right-click desktop, go to Properties, then the Advanced tab. Bottom left, there will be a resolution slider, and above it will say some monitor name on video card name, we need those. For instance, it can look like "Samsung 957 MB SyncMaster Magic on GeForce FX 5700".