A modern PC with Vista Home Edition takes about one and a half minutes to boot. An older machine with XP is about the same. That’s 30 seconds for the PC itself (the BIOS) to boot up, plus a minute for the Windows operating system to boot. Sometimes, you need to reboot Windows (e.g. when installing new software), but there is no need to restart BIOS, too. However, the default is to reboot both. (That’s called doing a “cold boot,” rather than a “warm boot.”) There’s a trick that works on both XP and Vista to get it to do a warm boot instead, thus saving you 30 seconds per cycle.
more and via: pctipsbox