What is Fastfat?
The genuine Fastfat.sys file is a software component of Microsoft Windows Operating System by Microsoft Corporation.
"FastFAT.sys" is Microsoft's driver used by Windows operating systems for accessing storage on devices that use File Allocation Table organization instead of the NTFS disk storage organization used by Windows NT. This includes floppy disks, USB flash drives, and most digital cameras. "FastFAT.sys" is in "C:\Windows\System32\drivers" and the system loads it using an API called IFS (Installable File System). By moving FAT driver logic outside the kernel into 32-bit PE executables, Microsoft achieved massive optimization, thus the "FastFAT" name. Booting with USB flash drives attached can sometimes cause BSOD's attributed to FastFAT.sys; removing them may resolve the problem.
FastFAT stands for Fast File Access Table Device Driver
Fastfat.sys is a Windows driver. A driver is a small software program that allows your computer to communicate with hardware or connected devices. This means that a driver has direct access to the internals of the operating system, hardware etc.
The free file information forum can help you determine if Fastfat.sys is a Windows system file or if it belongs to an application that you can trust.
Run a free scan to check for Fastfat drivers in need of updating
Fastfat.sys file information
The process known as Fast FAT File System Driver belongs to software Microsoft Windows Operating System by Microsoft (www.microsoft.com).
Description: The original Fastfat.sys is an important part of Windows and rarely causes problems. Fastfat.sys is located in the C:\Windows\System32\drivers folder.
Known file sizes on Windows 10/11/7 are 143,744 bytes (80% of all occurrences), 142,336 bytes or 143,360 bytes. 
The driver can be started or stopped from Services in the Control Panel or by other programs.
It is a Windows core system file. The program is not visible. The service has no detailed description. The Fastfat.sys file is a trustworthy file from Microsoft.
Fastfat.sys appears to be a compressed file.
Therefore the technical security rating is 0% dangerous, but you should also take into account the user reviews.
Recommended: Identify Fastfat.sys related errors
Important: Some malware disguises itself as Fastfat.sys, particularly when not located in the C:\Windows\System32\drivers folder. Therefore, you should check the Fastfat.sys process on your PC to see if it is a threat. We recommend Security Task Manager for verifying your computer's security. This was one of the Top Download Picks of The Washington Post and PC World.
Best practices for resolving Fastfat issues
A clean and tidy computer is the key requirement for avoiding problems with Fastfat. This means running a scan for malware, cleaning your hard drive using 1cleanmgr and 2sfc /scannow, 3uninstalling programs that you no longer need, checking for Autostart programs (using 4msconfig) and enabling Windows' 5Automatic Update. Always remember to perform periodic backups, or at least to set restore points.
Should you experience an actual problem, try to recall the last thing you did, or the last thing you installed before the problem appeared for the first time. Use the 6resmon command to identify the processes that are causing your problem. Even for serious problems, rather than reinstalling Windows, you are better off repairing of your installation or executing the 7DISM.exe /Online /Cleanup-image /Restorehealth command. This allows you to repair the operating system without losing data.
To get your computer running as fast as it did on day one, you can 8reset your PC. Your personal files will remain intact, but any programs you installed will need to be reinstalled.
To help you analyze the Fastfat.sys process on your computer, the following programs have proven to be helpful: ASecurity Task Manager displays all running Windows tasks, including embedded hidden processes, such as keyboard and browser monitoring or Autostart entries. A unique security risk rating indicates the likelihood of the process being potential spyware, malware or a Trojan. A good Bantivirus software detects and removes sleeping spyware, adware, Trojans, keyloggers, malware and trackers from your hard drive.
Other processes
mcods.exe asapiw2k.sys w3itemplatex.dll Fastfat.sys asussoftwaremanageragent.exe rcservice.exe gdkbb64.sys rdcfg.exe procexp151.sys csraudioguictrl.exe smss-doooms.vbs [all]
Score
User Comments
James Urwiller, Service Manager Computer Warehouse #4 (further information)
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Summary: Average user rating of Fastfat.sys: based on 17 votes with 11 user comments. 13 users think Fastfat.sys is essential for Windows or an installed application. 2 users think it's probably harmless. One user suspects danger. One user thinks Fastfat.sys is dangerous and recommends removing it. One user is not sure about it.