While listening to music in the background and working with graphics (CorelDRAW X4, Adobe Acrobat 3D), the sound crackles when scrolling or more complicated operations are performed. When the cracks are heard, Windows Task Manager shows visible peaks in CPU usage. The sound card is Creative Audigy 2 and the graphics card is ATI Radeon HD3650. The problem occurs only in Vista (32-bit, SP1) and not in XP on the same computer.
UPDATE: I solved the problem by removing the graphics card and using the integrated graphics chip on the motherboard.