Prefetch -
Windows Prefetch files, introduced in Windows XP, are designed to speed up the application startup process. Prefetch files contain the name of the executable, a Unicode list of DLLs used by that executable, a count of how many times the executable has been run, and a timestamp indicating the last time the program was run. Although Prefetch is present in Windows 2003, by default it is only enabled for boot prefetching. The feature is also found in Windows Vista, where it has been augmented with SuperFetch, ReadyBoot, and ReadyBoost.
From Windows PC Accelerators:
SuperFetch; analyzes per-machine usage patterns over time and optimizes the data that is kept in memory.
ReadyBoot; decreases boot time (the time from turning power on to reaching the log-on screen) by preloading the files and startup programs needed per-machine into a cache.
ReadyBoost; supports the use of flash storage devices like Universal Serial Bus (USB) flash drives and Secure Digital (SD) flash cards to boost PC performance.
ReadyDrive; supports hybrid hard disk drives.
For SSD drives Prefetch is disabled by default.
Prefetch files
The Prefetch files are stored in the directory:
%SystemRoot%\Prefetch 
The following files can be found in the Prefetch directory:
*.pf, which are Prefetch files;
Ag*.db and Ag*.db.trx, which are SuperFetch files;
Layout.ini;
PfPre_*.db;
PfSvPerfStats.bin
A Prefetch file contains the name of the application, a dash, and then an eight character hash of the location from which that application was run, and a .pf extension. The filenames should be all uppercase except for the extension. E.g. a filename for md5deep would look like: MD5DEEP.EXE-4F89AB0C.pf. If an application is run from two different locations on the drive (i.e. the user runs C:\md5deep.exe and then C:\Apps\Hashing\md5deep.exe), there will be two different prefetch files in the Prefetch folder. According to MSDN up to 128 Prefetch files can be stored in the Prefetch directory 2.
File format
Each Prefetch file has a 4-byte signature (at offset 4) "SCCA" (or in hexadecimal notation 0x53 0x43 0x43 0x41). The signature is assumed to be preceded by a 4-byte format version indicator:
17 (0x00000011) for Windows XP and Windows 2003
23 (0x00000017) for Windows Vista, Windows 2008, Windows 7 and Windows 2012 (note Windows 2012 has not been confirmed)
26 (0x0000001a) for Windows 8.1 (note this could be Windows 8 as well but has not been confirmed)
30 (0x0000001e) for Windows 10
For more information about the file format see: Windows Prefetch File Format
The Prefetch file contains various metadata.
The executable's name, up to 29 characters.
The run count, or number of times the application has been run.
Volume related information, like volume path and volume serial number.
The size of the Prefetch file (sometimes referred to as end of file (EOF)).
The files and directories that were used doing the application's start-up.
Timestamps
The Prefetch file contains 2 types of timestamps
The time when the application was last ran (executed). Version 26 of the Prefetch format maintains 7 previous last run times.
The volume creation time (part of the volume information) of the volume the Prefetch file was created on.
The file system creation time of the Prefetch file indicates the first time the application was executed. Both the file system modification time of the Prefetch file and the embedded last run time indicate the last time the application was executed.
Prefetch hash
There are multiple known hashing functions to be used for prefetch file filename hashing, namely:
SCCA XP hash function; used on Windows XP and Windows 2003
SCCA Vista hash function; used on Windows Vista
SCCA 2008 hash function; used on Windows 2008, Windows 7, (possibly: Windows 2012) and Windows 8 (including 8.1)
SCCA XP hash function
A Python implementation of the SCCA XP hash function:
def ssca_xp_hash_function(filename): hash_value = 0 for character in filename: hash_value = ((hash_value * 37) + ord(character)) % 0x100000000 hash_value = (hash_value * 314159269) % 0x100000000 if hash_value > 0x80000000: hash_value = 0x100000000 - hash_value return (abs(hash_value) % 1000000007) % 0x100000000 
SCCA Vista hash function
A Python implementation of the SCCA Vista hash function:
def ssca_vista_hash_function(filename): hash_value = 314159 for character in filename: hash_value = ((hash_value * 37) + ord(character)) % 0x100000000 return hash_value 
SCCA 2008 hash function
A Python implementation of the SCCA 2008 hash function:
def ssca_2008_hash_function(filename): hash_value = 314159 filename_index = 0 filename_length = len(filename) while filename_index + 8 < filename_length: character_value = ord(filename[filename_index + 1]) * 37 character_value += ord(filename[filename_index + 2]) character_value *= 37 character_value += ord(filename[filename_index + 3]) character_value *= 37 character_value += ord(filename[filename_index + 4]) character_value *= 37 character_value += ord(filename[filename_index + 5]) character_value *= 37 character_value += ord(filename[filename_index + 6]) character_value *= 37 character_value += ord(filename[filename_index]) * 442596621 character_value += ord(filename[filename_index + 7]) hash_value = ((character_value - (hash_value * 803794207)) % 0x100000000) filename_index += 8 while filename_index < filename_length: hash_value = (((37 * hash_value) + ord(filename[filename_index])) % 0x100000000) filename_index += 1 return hash_value 
/prefetch flag
From: Misinformation and the The Prefetch Flag
The /prefetch:# flag is looked at by the OS when we create the process — however, it has one (and only one) purpose. We add the passed number to the hash. 
It appears that the following are equivalent on Windows 10 1903 and 2004:
Notepad.exe
Notepad.exe /prefetch:0
Notepad.exe /prefetch:9
So that /prefetch:[0-8] only seem to be the supported values and the /prefetch:9 and larger are equivalent to /prefetch:0
Registry Keys
Key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Memory Management\PrefetchParameters 
The EnablePrefetcher Registry value can be used to disable prefetch.
See Also
Prefetch XML
ReadyBoot
SuperFetch
Windows
Windows Prefetch File Format
External Links
Wikipedia Prefetcher
MSDN: Disabling Prefetch
Windows XP: Kernel Improvements Create a More Robust, Powerful, and Scalable OS, by Mark Russinovich, David Solomon, December 2001
Prefetch file metadata, by Harlan Carvey, July 13, 2005
Prefetch files, revisited, by Harlan Carvey, April 13, 2006
Windows Memory Management, by logicchild, September 17, 2008
Windows Memory Management - Part 2, by logicchild, September 25, 2008
De-mystifying Defrag: Identifying When Defrag Has Been Used for Anti-Forensics (Part 1 - Windows XP), by Chad Tilbury, August 5, 2009
Windows Prefetch File (old blog entry from 42 LLC), by Yogesh Khatri, April 14, 2010
Windows PC Accelerators
Decoding Prefetch Files for Forensic Purposes: Part 1, by Mark Wade, December 8, 2010
Prefetch Files at Face Value, by Mark Wade, April 11, 2011
Windows Logical Prefetcher, TTS blog, July 30, 2011 (article is in Russian)
Prefetch i niedokładny licznik by Paweł Hałdrzyński, August 20, 2011 (article in Polish; uncertain about the year of publication)
Prefetch Analysis, Revisited, by Harlan Carvey, March 8, 2012
Prefetch Analysis, Revisited...Again..., by Harlan Carvey, March 15, 2012
Prefetch Hash Calculator + a hash lookup table xp/vista/w7/w2k3/w2k8, Hexacorn blog, June 13, 2012
Prefetch file names and UNC paths, Hexacorn blog, October 29, 2012
NTOSBOOT Prefetch File, by Corey Harrell, December 5, 2012
What's New in the Prefetch for Windows 8??, by Jared Atkinson, September 21, 2013
Windows Prefetch (.PF) files, by Yogesh Khatri, October 21, 2013
Windows Systems and Artifacts in Digital Forensics: Part III: Prefetch Files, by Ivan Dimov, November 21, 2013
Prefetch 101 - a Windows 8 Prefetch file walkthrough, by Jared Atkinson, 2014
A first look at Windows 10 prefetch files, by Francesco Picasso, June 22, 2015
Tools
Free - Non Open Source
Windows File Analyzer - Parses Prefetch files, thumbnail databases, shortcuts, index.dat files, and the recycle bin
CrowdResponse
Open Source
libscca
prefetch-tool, Script to extract information from windows prefetch folder
Plaso
PECmd, Prefetch command line tool using Prefetch, Prefetch parser written in C# with support for XP through Windows 10 - Needs WINAPI for decompression