BootVis is a Microsoft computer application that allows "PC system designers and software developers" (not aimed at end-users) to check how long a Windows XP machine takes to boot, and then to optimize the boot process, sometimes considerably reducing the time required.
The application measures time taken during Windows XP's boot or resume period.
BootVis can also invoke the optimization routines built into Windows XP, such as defragmenting the files accessed during boot, to improve startup performance.
[3] Because the Global Logger session used by BootVis is triggered by registry entries, it runs every time that the entries appear in the registry, which has resulted in some users seeing large quantities of hard drive being used for the trace.log file (in C:\WINDOWS\System32\LogFiles\WMI).
The user can run BootVis again and click Trace→Stop Tracing, which will stop the file from growing and allow it to be safely deleted.