What is the "Startup impact" column in Task Manager?

Solution 1:

This is a special measurement based on an application's CPU and disk usage during startup. It helps the user to determine what app slows down the startup process and to decide what to disable.

The official documentation at Microsoft website states that these values are possible:

• High impact – Apps that use more than 1 second of CPU time or more than 3 MB of disk I/O at startup
• Medium impact – Apps that use 300 ms - 1000 ms of CPU time or 300 KB - 3 MB of disk I/O
• Low impact – Apps that use less than 300 ms of CPU time and less than 300 KB of disk I/O

Moreover, you can see the exact CPU and disk I/O utilization values yourself by enabling the corresponding columns on the same tab:

P.S. The 'Startup' tab has actually been in previous versions of Windows. It was less fancier though and could be found in the msconfig applet. In Windows 8 the corresponding msconfig tab redirects user to the Task Manager: