However, in my case, my browser starts up with less time than letting me use a stopwatch while I disabled the Prefetch function...
This can happen if prefetching was never enabled properly to begin with or disabled and never properly renabled. Try this, BootVis is the most accurate way to time startup:
Testing Prefetching At BootupEnable Prefetching and Test1. Services
Task Scheduler = Automatic
COM+ Event System = Automatic
2. Registry (Using Regedit)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters
Name: EnablePrefetcher
Type: REG_DWORD
Value: 3
3. Reboot three times.
4. Download and Run BootVis. In the menu go to "Trace", select "Next Boot and Driver trace". A "Trace Repetitions" screen will appear, select "Ok" and Reboot. Upon reboot, BootVis will automatically start, analyze and log your system's boot process. When it's done, in the menu go to "Trace" and select "Optimize System" and Reboot. This time when your system comes up, wait until you see the "Optimizing System" box appear, continue to wait until the process is complete.
5. Now you system is optimized for Prefetching run BootVis, go to "Trace", select "Next Boot". Record the time.
Note: You need to confirm Prefetching is working by looking in the C:\Windows\Prefetch folder. For Boot Prefetching you should see a NTOSBOOT-xxxxxxxx.pf and a layout.ini file in the folder. If not prefetching is not working. The built-in Disk Defragmenter needs to be installed and operational (nLite users) Otherwise BootVis can invoke the layout optimization. By default Windows does this every three days, for testing or anytime you want an immediate improvement, say you added or removed a startup option use BootVis and the "Optimize System" option.
Disable Prefetching and Test1. Registry (Using Regedit)
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters
Name: EnablePrefetcher
Type: REG_DWORD
Value: 0
2. Run BootVis, go to "Trace", select "Next Boot". Record the time.
Note: These steps are necessary only to confirm your system is setup to use prefetching properly and for this test. On a regular (non tweaked) XP install (not nLite) the Prefetcher is enabled by default, the two services set to automatic, the disk defragmenter is installed and the Registry Key set to 3. After three regular boots it will automatically take effect and after three days layout the files automatically and continue to do so automatically. The problem is with certain tweak programs or custom installs that break the Prefetcher. In which case the steps to enable prefetching above should get you back to normal, if all the features are there (no guarantees with an nLite install).