Startup Time is not really a factor when you judge the performance of an Operating System because most power users start their computer only once a day. But its an important cosideration for an average user who uses his computer for short intervals spread over different times in the day. He will expect the computer to start as fast as possible. Another consideration is the fact that Start-up and Shut-down times are the first directly measurable indication of OS's speed.
We tested all the three Operating systems on a laptop with 2.4 GHz (P8400) Centrino 2 processor, 4 GB of RAM at 800 MHz FSB and a 7200 RPM hard-disk drive. Windows 7 took 23 seconds to bring the desktop, whereas XP took 27 seconds and Vista faired a high 34 seconds. Now, there is a difference betweek appearance of the Desktop and the full startup of an Operating system since a lot of services in Windows 7 and Vista are scheduled to 'delay-start'. To compare that, we started Windows and measured the time it took to connect to the internet, Open Internet Explorer and open Google.com Homepage. Windows 7 gets to work quickly and after the appearance of the desktop it took only a further 3 seconds to display the Google homepage. Compared to this, Vista took more than 8 seconds and XP took a competitive 4 seconds. The whole startup process for Windows 7 up to the appearance of Google took 26 seconds. Vista takes 42 seconds and XP 31 seconds.
Windows 7 also shuts down quicker than its two predecessors, taking just 6 seconds compared with 9 seconds for Vista and just a bit more than 6 seconds for XP.
Overall, the startup and shutdown timings show that Windows 7 performs best in a clean install. XP comes a close second and Vista a distant third. However, updates, security patches and application installations may alter those timings.