Have you tried a spyware removal program? You may also be able to try a system restore instead of completely reinstalling Windows. Repairing Windows through your Windows installation CD may or may not work as well. Have you tried reinstalling PSP6? Also, check your file associations in Windows Explorer/Tools/Folder Options/File Types (I think that's right, since I'm currently using a Chinese Windows) to see if there are some messed up associations with your image files.
Or you can try right-clicking each image type one by one, and use Open As, then choosing your program (PSP6 or CorelDraw), and saying to always open with this.