The Vista Transformation Pack (or VTP) is a pack developed by the coder WindowsX. Currently in its 8th version, it is the only known pack to fully and accurately emulate Windows Vista. VTP emulates the transparency effect, the Start menu, clock style, Flip3D and even the Sidebar by using various third-party applications. Installation is pretty simple; just run the installer and keep clicking 'Next'.
Use the 'Classic' install mode so that you can select which third-party applications you want installed. You will get the best Vista experience if you check all options. However, this pack when installed with all its features tends to hog a lot of system memory. Therefore, install only those applications that are needed.
The VTP changes literally everything about your Windows XP to make it look like Vista, to the extent of even changing the boot screen and the logon screen. You also have a Vista 'Welcome Center' after every reboot.