dwm.exe is known for using much CPU. It's the process that creates the live thumbnails, transparent windows and so on in Aero. If you have several applications active, it will use a lot of memory and CPU to keep track of actual window layout for each application.
If you have an older computer, this can cause the computer to get slow. If there are other processes which are using much CPU, just post them. You also could post some specifications like processor memory and graphics card.
Actually I don't think you still have spyware on your computer. To speed up a little you should turn of Aero, which will free up system resources, but you'll also loose some of the nice graphics
Stäng ner lite grafikalternativ i Vista