BootTimer is a free application which can measures Windows startup times.
BootTimer will not calculate the time taken to go through BIOS, and will start immediately when your PC starts loading Windows. Currently, BootTimer works on Windows NT, Windows XP and Windows XP 64 bit Edition, and yet to support Windows Vista.
To use BootTimer, launch the application and a messagebox will appear and ask you to reboot your Windows. After you click “Yes”, your computer will restarts. After your computer restarts, you will get another messagebox that show you the total time taken to start Windows.
download BootTimer | download from MediaFire
Source: gHacks
This is really a helpful utility. Previously I used to calculate via BootViz .. now I can do it easily with this utility