Image file (PaintShop Pro)
Paint Shop Pro is a less expensive alternative to Adobe Photoshop. Formerly owned by Jasc, PSP was acquired by Corel in October 2004 is now called Paint Shop Photo Pro X3 and currently uses different file extensions.
The PSP file extension is also associated with the Prodea Synergy procedure file format.
Learn more about PSP files:
Wikipedia has an entry on PSP files
Visit the Paint Shop Photo Pro X3 website.
Find an answer for a PSP Question at IT Knowledge Exchange.