What is vmm?

The genuine vmm.sys file is a software component of Microsoft Virtual Server by Microsoft.
"vmm.sys" is a Windows kernel driver for Microsoft Virtual Server software. This driver gets referenced whenever program components or system modules need to use or access any Microsoft Virtual Server functions. The file basically monitors and controls all operations of PC drivers to handle compatibility from within. It listens and responds to requests or actions from various Windows components or operating systems. Microsoft has integrated this virtual machine functionality within Windows to allow integration between different Windows Operating Systems or other software needing compatibility with the current OS and the current drivers. This is especially needed in networks with various versions of Windows or other operating systems. Microsoft is a global software and hardware company, developing useful technology for both consumers and businesses since 1975.

VMM stands for Virtual Machine Monitor

Vmm.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 vmm.sys is a Windows system file or if it belongs to an application that you can trust.

Run a free scan to check for vmm drivers in need of updating

Vmm.sys file information

The process known as Virtual Machine Monitor belongs to software Microsoft Virtual Server (version 2005 R2 SP1) or Virtual PC or Microsoft Virtual (version PC 2004) by Microsoft (

Description: Vmm.sys is not essential for Windows and will often cause problems. Vmm.sys is located in the C:\Windows\System32\drivers folder. Known file sizes on Windows 10/8/7/XP are 232,816 bytes (30% of all occurrences), 147,040 bytes and 4 more variants. 
The driver can be started or stopped from Services in the Control Panel or by other programs. The program is not visible. It is certified by a trustworthy company. There is no detailed description of this service. The file is not a Windows core file. vmm.sys appears to be a compressed file. Therefore the technical security rating is 26% dangerous, however you should also read the user reviews.

Uninstalling this variant: If you encounter difficulties with vmm.sys, you can also remove the entire program Microsoft Virtual PC 2007 or Virtual Machine Monitor using Windows Control Panel or consult Microsoft's Customer Service [1][2].

Recommended: Identify vmm.sys related errors

Important: Some malware camouflages itself as vmm.sys. Therefore, you should check the vmm.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.


User Comments

Part of Microsoft Virtual Machine
  tmahn642   (further information)
My antivirus detected this and another driver as a hidden driver and rootkit
It's nonessential, but it can be forged by some viruses, like the one that hijacks your browser to

Summary: Average user rating of vmm.sys: based on 3 votes with 3 user comments. One user thinks it's probably harmless. One user thinks it's neither essential nor dangerous. One user suspects danger.

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Best practices for resolving vmm issues

A clean and tidy computer is the key requirement for avoiding problems with vmm. This means running a scan for malware, cleaning your hard drive using cleanmgr and sfc /scannow, uninstalling programs that you no longer need, checking for Autostart programs (using msconfig) and enabling Windows' Automatic 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 resmon 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, for Windows 8 and later versions, executing the DISM.exe /Online /Cleanup-image /Restorehealth command. This allows you to repair the operating system without losing data.

To help you analyze the vmm.sys process on your computer, the following programs have proven to be helpful: Security 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. Malwarebytes Anti-Malware detects and removes sleeping spyware, adware, Trojans, keyloggers, malware and trackers from your hard drive.

Other processes

vmm.sys [all]