How do I fix illegal operation

Cause

Illegal Operations can be caused by several different factors. Below is a listing of the more commonly known reasons for getting an Illegal Operations.

1. TSR's or Third-party programs causing memory conflicts or other conflicts with the program or programs attempting to be run.
2. Data not being read properly from source. Running a program or game with a dirty CD can cause the CD to be read improperly causing Illegal Operations. Floppy diskettes, which may contain errors can cause illegal operations.
3. Installing a program or game on a hard disk drive that has errors or is highly fragmented.
4. Corrupt files.
5. Memory managers.
6. Bad, incorrect or not the latest video drivers.
7. Computer Virus.
8. Added hardware
9. Error in program coding
10. Corruption or problem within Windows.
11. Bad Memory, invalid bits or physically bad memory.

Solution

TSR's or Third-party programs

TSR's or Third-party programs running in the background are one of the more commonly found reasons for Illegal Operations. If you are receiving an Illegal Operation when attempting to run a game or program it is recommend that you temporarily remove or disable programs running and TSR's running in the background, ensuring that these programs are not causing your issues.

• How to remove TSRs and startup programs.

If, after removing these programs, you run the program or game and no longer receive the Illegal Operations, it is recommend that you reboot the computer and disable or End Task each program or TSR one at a time to attempt to determine what program is causing the Illegal Operation.

Data not being read properly from source

When running a program or game from a CD you receive an Illegal Operation, verify that the CD is clean. Additional information on how to clean a CD or CD-ROM drive can be found on our Cleaning Page.

If you are running a game from a floppy diskette or other floppy media such as a zip diskette or LS120, verify that the diskette does not have physical errors with it by running a ScanDisk or a disk drive utility included with the drive.

Installing a program or game on a hard disk drive that has errors or is highly fragmented

When installing a program or game onto a hard disk drive it is recommended if you receive errors after installing that program or game that you uninstall that program or game, run a ScanDisk, then a defrag, and finally install the program or game again.

If errors exist on the hard disk drive, they will cause the program or game to run improperly and can cause Illegal Operations.

• Microsoft ScanDisk help page.
• Microsoft Defrag help page.

Corrupt files

Corrupt, bad or missing files can cause Illegal Operations. It is recommended that you uninstall or reinstall the program causing the Illegal Operation to verify that any corrupt, bad or missing files are replaced or repaired during the reinstallation.

Memory managers

If you are running a memory manager that is used to obtain more memory or handle the computer memory in replace of Windows, it is recommended you temporarily disable or uninstall this program to verify it is not the memory manager causing the Illegal Operations. 

Bad, incorrect or not the latest video drivers

Bad, incorrect or not the latest video drivers may cause Illegal Operations when performing such tasks as moving the mouse or dragging data from one source to another as high demands are placed onto the video card. Decrease the video settings to at least 800 x 600, 256 colors to verify if the program or game being run is having errors because of the current video settings.

• How to set the resolution in Microsoft Windows?
• How to set the resolution or change the resolution/adapter in Windows 3.x.

If, after attempting to adjust the video settings, you still encounter the same issue, verify the computer is utilizing the latest video card drivers by visiting our computer video drivers section.

Computer Virus

Because computer viruses are loaded into memory and can change the data of program files when infecting a computer, ensure that a virus protection utility is installed on the computer and that you have the latest Virus Definition.

Additional information about computer Viruses can be found at our Virus page.

Added hardware

If added hardware has been recently installed onto the computer it is likely that either the hardware is conflicting with other hardware devices on the computer or that the drivers used to install that hardware is causing issues with other hardware or software installed on the computer.

If added hardware has recently been added to the computer, it is recommended that you temporarily remove that added hardware and the software associated with it to ensure it is not causing your issues. 

Error in program coding

If you are receiving Illegal Operations only when running a particular program, verify that the program is compatible with the Version of Windows you are running and ensure no available patches or software are available that may fix errors made during the development stages.

Corruption or problem within Windows

Because Windows controls the memory operations as well as the file structure and association, it is possible for Windows or files associated with Windows to become corrupted, causing Illegal Operations or other errors. It is recommended you reinstall Windows if you are experiencing Illegal Operations in Windows or more than one program trying to be run on the computer.   

Bad Memory, invalid bits or physically bad memory

It is possible that bad memory can cause Illegal Operations. If you have recently added memory to the computer, it is recommended that it first be removed to verify that you are not experiencing conflicts with the recently installed memory.

If no memory has been recently added to the computer and you have tried all the above recommendations test your computer memory.