CS4 features smoother panning and zooming, allowing faster image editing at a high magnification. The interface is more simplified with its tab-based interface making it cleaner to work with. Photoshop CS4 features a new 3D engine allowing the conversion of gradient maps to 3D objects, adding depth to layers and text, and getting print-quality output with the new ray-tracing rendering engine. It supports common 3D formats; the new Adjustment and Mask Panels; Content-aware scaling (seam carving); Fluid Canvas Rotation and File display options.The Content-aware scaling allows users to intelligently size and scale images, and the Canvas Rotation tool makes it easier to rotate and edit images from any angle.
Adobe released Photoshop CS4 Extended, which has the features of Adobe Photoshop CS4, plus capabilities for scientific imaging, 3D, motion graphics, accurate image analysis and high-end film and video users. The faster 3D engine allows users to paint directly on 3D models, wrap 2D images around 3D shapes and animate 3D objects. As the successor to Photoshop CS3, Photoshop CS4 is the first x64 edition of Photoshop on consumer computers for Windows. The color correction tool has also been improved significantly.
CS4 and CS4 Extended were released on October 15, 2008. They were also made available through Adobe’s online store and Adobe Authorized Resellers. Both CS4 and CS4 Extended are offered as either a stand-alone application or feature of Adobe Creative Suite. The price for CS4 is US$699 and the extended version is US$999. Both products are compatible with Intel-based Mac OS X and PowerPCs, supporting Windows XP and Windows Vista.
As this is portable version, you don't have to download the software.
Just run the software and it will open directly without installation.