Anyone who's owned a computer for an extended period of time (1+ years) can tell you that, after some amount of time, it just seems to boot up much slower than when they first got it. There are plenty of ways to help keep your computer's boot time as small as possible, but how can you find out exactly how long your system is taking to boot up? Check these steps out to find this information built right into a Windows utility.
Step 1: Open the Start menu and type Event viewer into the Search box and open the application.
Step 2: In the left pane of the Event Viewer, navigate the folders to Applications and Services Logs/Microsoft/Windows/Diagnostics-Performance.
Step 3: Expand this entry and double click on Operational (it should be the only thing in this folder) to see a full diagnostic report of your computer's operation.
Step 4: Click Filter Current Log in the pane to the right. In the window that appears, change "<All Event IDs>" (the text box above the one labeled Task category) to "100." Click OK to apply the filter.
The list in the center pane will now show information about each boot process.
Step 5: Select a specific event to see more information about that particular boot sequence.
For total boot time: Look in the pane that appears below this list; the value next to "Boot Duration" is the amount of time (in ms) that your system took to load from start to finish. Just divide by 1000 to get the time in seconds.