Windows Boots Slowly: Measure Before You Change

Slow boot attracts more unfounded advice than almost any other Windows complaint, most of it consisting of registry changes and service disablings passed between forums. The reason it persists is that nobody measures. Without a number before and after, any change appears to have worked.

Measure First

Windows records boot performance. Event Viewer holds a diagnostics performance log that logs each boot with a total duration and a breakdown of what consumed it, including specific services and applications that caused delays.

That log gives three useful things: a baseline, an itemised account of where the time went, and a way to confirm whether a change helped.

Start there. Most of what follows is unnecessary if the log names a single component responsible for most of the duration.

Startup Impact

Task Manager’s startup tab lists what launches with the user session and rates each entry’s impact. Sorting by that rating puts the expensive items at the top.

Disabling a startup item stops it launching automatically; it does not uninstall it, and the application still runs when opened. That makes this a low-risk change and a reversible one.

The effect is often smaller than expected, because user startup items run after the desktop appears. They make the machine feel slow to become usable rather than slow to boot, which is a real complaint but a different one.

Services and Drivers

Much of boot duration is services starting and drivers initialising, and this is where the event log earns its place. A driver that times out during initialisation can consume a large share of the total, and nothing in Task Manager would show it.

Services set to start automatically can be switched to delayed start, which lets the desktop appear before they run. That does not reduce total work but it changes when it happens, which is usually what the user actually wants.

Disabling services wholesale is where this goes wrong. Each one exists for something, and the search service, the update service and the print service are all frequently recommended for disabling by people who then lose search, updates and printing.

Fast Startup

Fast Startup saves the kernel session to disk when the machine shuts down and restores it on the next power-on rather than initialising from scratch. On a mechanical drive the saving is substantial.

It also means a shutdown is not a full shutdown. This has consequences that are not obvious:

This is why some problems clear after a restart but survive a shutdown, which is the reverse of the usual assumption.

Disable it while troubleshooting boot behaviour, so that each start is a real one. On a machine with solid state storage the saving it provides is small enough that leaving it off is a reasonable permanent choice.

The Storage Itself

Boot is a burst of reads. A mechanical drive services them one at a time, which is why boot on a spinning disk is slow in a way no configuration change resolves.

A drive that is failing is worse, because sectors that need retrying take far longer than normal reads. If slow boot is accompanied by freezes during use, disk warnings in the event log, or very high response times under load, treat the hardware as the cause.

In that case, copy irreplaceable data off before running any repair. A surface scan on a struggling drive applies sustained load at the worst possible time, and data in sectors that cannot be read is not recovered by marking them bad. See chkdsk, SFC and DISM for what each repair does.

Firmware Time

Some of the delay may be before Windows starts at all. Firmware initialisation, device enumeration and boot device selection all take time, and none of it is affected by anything done inside Windows.

If the delay is between power-on and the Windows logo, the settings to look at are in firmware: the boot order, whether network boot is being attempted and timing out, and whether fast boot options exist at that level.

Timing the two phases separately is worth thirty seconds, because it decides whether to look inside Windows at all.

What People Get Wrong About This

The first mistake is making changes without measuring, which makes every change appear successful.

The second is applying lists of service disablings from forums. They trade features for a saving that is usually small and sometimes zero, and the lost functionality is discovered weeks later.

A third is confusing slow boot with slow login. Time from power-on to the login prompt and time from login to a usable desktop have different causes; the second is dominated by user startup items and profile loading.

A fourth is troubleshooting boot with Fast Startup enabled, so that each test restores a saved session rather than performing the boot being investigated.

And the last is ignoring the possibility of a failing drive because the machine is otherwise usable. Boot is the heaviest read burst the machine performs and it is where a struggling drive shows first.

A Working Order

Time the firmware phase and the Windows phase separately. Read the boot performance log for a named culprit. Check startup impact. Disable Fast Startup and measure a genuine boot. Consider delayed start for services that are not needed immediately. Then, if the number has not moved, look at the drive.