I just did a clean install and updated Windows XP and AutoCAD. The mouse movement is always smooth and when selecting icons on the desktop or using the left click on the desktop to make a bounding box again all is fast and smooth. Whenever I click on the AutoCAD window there is a small pause to everything in AutoCAD really. I’ve found many threads on the mouse movement being an issue and setting the “Optimize mouse for games” option to never being the fix. In my setup though the mouse movement is still very smooth and fast in AutoCAD but when you try to draw a bounding box it lags for a second and when you try to double click it lags for a second and so on. It makes getting any work done really painful.
The PC is new so it really should be much faster than it is.