Does scandisk/chkdsk produce a log file when running before login?
On boot up, chkdsk saves its results to the Event Log.
Using Event Viewer to Find Chkdsk Results
After CHKDSK has run and your machine has rebooted, run the event
viewer: hold down the Windows key and press R, and type eventvwr
into the resulting Run dialog.
Click on OK and Event Viewer will run.
This is the Windows 8 Event Viewer; Windows 7’s and Vista’s are
similar, while Windows XP’s is actually much simpler. While the screen
shots may be different, the general idea will apply to all three.
If the right-hand pane bothers you, as it does me, click on the
“Show/Hide Action Pane” toolbar button to make it go away.
Expand the “Windows Logs” on the left (by clicking on the triangle to
its left), and click on “Application” below it.
In the event log list that appears to the right, click on the first
item, and then, one at a time, press the down-arrow key to see each
successive event. You’re viewing them in reverse-chronological order
(most recent first). There will be many that are basically
incomprehensible – don’t worry about them. There may be several that
display scary red “error” icons – ignore those too, they’re part of
the mess that is the Event Viewer.
Eventually you’ll come to an event with its “Source” listed as Wininit
(Windows Initialization). The information displayed in the window
below will look very familiar (there may be many other events from
Wininit; we’re looking for the one that has CHKDSK information in the
event information below the list).
Note: as pointed out in the answer from @Wessel, the Windows XP event source to look for is "winlogon".
The text box within the “General” tab of that information below the
event-log listing is scrollable, and contains the entire text of the
CHKDSK run that happened at boot time. You can scroll up and down to
view the entire CHKDSK session.
An easier way to view the entire CHKDSK result is to click anywhere on
the results text, type CTRL+A to select all, then CTRL+C to copy it
all to the clipboard. Now run Notepad, and paste the results in there.
The formatting can sometimes be a
little odd, but the results are exactly what you’d expect: the text
generated by CHKDSK as it ran on boot. It’s all there for you to view
at your leisure.
Source How do I see the results of a CHKDSK that ran on boot?