What is isapnp?

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

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Isapnp.sys file information

The process known as PNP ISA Bus Driver or PnP ISA/EISA Bus Driver belongs to software Microsoft Windows Operating System or Betriebssystem Microsoft Windows by Microsoft (

Description: Isapnp.sys is an important part of Windows, but often causes problems. The isapnp.sys file is located in the C:\Windows\System32\drivers folder. Known file sizes on Windows 10/8/7/XP are 37,248 bytes (53% of all occurrences), 35,840 bytes, 37,632 bytes or 37,504 bytes. 
The driver can be started or stopped from Services in the Control Panel or by other programs. It is a Windows system file. The program has no visible window. There is no detailed description of this service. Isapnp.sys is a trustworthy file from Microsoft. isapnp.sys appears to be a compressed file. Therefore the technical security rating is 3% dangerous, however you should also read the user reviews.

Recommended: Identify isapnp.sys related errors

Important: Some malware disguises itself as isapnp.sys, particularly when not located in the C:\Windows\System32\drivers folder. Therefore, you should check the isapnp.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

had 512Mb of Memory in 2 256Mb blocks. Removed 1 of them and started the PC, the PC shows this error when both blocks are in, but works when only 1 block is in.
isapnp.sys is a device driver that manages plug-and-play for old ISA type expansion slots.
isapnp.sys error often shows up when ram is corrupted. Find the damaged ram and swap it out
I agree with Ogre 100% I experianced the same thing $& remove one of these slots and there you go , The system has started again. Thanks Ogre
  Mohammad, Saudi Arabia  
It may not be essential for newer computers, but it is installed as a standard Windows file. If it is corrupt, it will cause startup to fail. Solution: Microsoft says replace it from the Windows install CD. Will the system start without it? Probably not, unless the registry is changed to allow it to be ignored.
  Lance in Shanghai   (further information)
I agree it's essential to windows, causing mostly boot problems if damaged, but i don't think its connected to RAM, but ISA plug'n'play expansion slots
Rootkit.Win32.TDSS.d was in it
yes if it is preventing from booting, or reinstalling windows, then it is a hardware issue. From my experience, one of your ram memory is bad. remove all of your ram memory, and restart your system with one stick only. repeat with one stick until you can single out which is the bad memory stick.
The error occurs due to a corrupted RAM. just try replacing it
  Michael   (further information)
This file runs my win 7 64 system and has for 6 months, masterfully I must say, and after 3 total (w/ fake HD formats) iso and orig. re-installs. My laptop is a brick.
  No Thanks  

Rating chart

Summary: Average user rating of isapnp.sys: based on 10 votes with 11 user comments. 4 users think isapnp.sys is essential for Windows or an installed application. 3 users think it's probably harmless. One user thinks it's neither essential nor dangerous. 2 users think isapnp.sys is dangerous and recommend removing it. 3 users don't grade isapnp.sys ("not sure about it").

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Best practices for resolving isapnp issues

A clean and tidy computer is the key requirement for avoiding problems with isapnp. 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 isapnp.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

isapnp.sys [all]