A senior member of the Windows 7 development team says that there is a team of engineers dedicated to start up performance that has set a goal of having a 15 second or less boot time. The post goes into detail about what it takes to achieve that goal and how the team is progressing. Here's an excerpt:

From our perspective, too few systems consistently boot fast enough and we have to do much better. Obviously the systems that are greater than 60 seconds have something we need to dramatically improve-whether these are devices, networking, or software issues. As you can see there are some systems experiencing very long boot times. One of the things we see in the PC space is this variability of performance-variability arises from the variety of choices, and also the variety of quality of components of any given PC experience. There are also some system maintenance tasks that can contribute to long boot times. If a user opts to install a large software update, the actual updating of the system may occur during the next boot. Our metrics will capture these and unfortunately they can take minutes to complete. Regardless of the cause, a big part of the work we need to do as members of the PC ecosystem is address long boot times.

Before discussing some of our Windows 7 efforts, we'd like to point out there is considerable engagement with our partners underway. In scanning dozens of systems, we've found plenty of opportunity for improvement and have made changes. Illustrating that, please consider the following data taken from a real system. As the system arrived to us, the off-the-shelf configuration had a ~45 second boot time. Performing a clean install of Vista SP1 on the same system produced a consistent ~23 second boot time. Of course, being a clean install, there were many fewer processes, services and a slightly different set of drivers (mostly the versions were different). However, we were able to take the off-the-shelf configuration and optimize it to produce a consistent boot time of ~21 seconds, ~2 seconds faster than the clean install because some driver/BIOS changes could be made in the optimized configuration. For this same system, it is worth noting the resume from sleep time is approximately 2 seconds, achieving a nearly instant on experience. We do encourage users to choose sleep as an alternative to boot.

As an example Windows 7 effort, we are working very hard on system services. We aim to dramatically reduce them in number, as well as reduce their CPU, disk and memory demands. Our perspective on this is simple; if a service is not absolutely required, it shouldn't be starting and a trigger should exist to handle rare conditions so that the service operates only then.  Of course, services exist to complete user experiences, even rare ones. Consider the case where a new keyboard, mouse or tablet HW is added to the system while it was off. If this new HW isn't detected and drivers installed to make the HW work during startup, then the user may not be able to enter their credentials and log into the machine. For a given user, this may be a very rare or never encountered event. For a population of 100s of millions of users, this can happen frequently enough to warrant having mechanisms to support it. In Windows 7, we will support this scenario and many others with fewer auto start services because more comprehensive service trigger mechanisms have been created.

In terms of reading files from the disk, Windows 7 has improvements in the 'prefetching' logic and mechanisms. Prefetching was introduced way back in Windows XP. Since today's disks have differing performance characteristics, the scheduling logic has undergone some changes to keep pace and stay efficient. As an example, we are evaluating the prefetcher on today's solid state storage devices, going so far as to question if is required at all. Ultimately, analysis and performance metrics captured on an individual system will dynamically determine the extent to which we utilize the prefetcher.