Hi all. I’m a new user of Avast 4.1 Home Edition (on a WinXP-SP2 o.s.) and I have a problem.
When I try to execute the dos command ‘edit.com’ from a command line, it appears a window with an error message:
“The NTVDM CPU has ecountered an illegal instruction…”
If I open the CONFIG.NT file and remove the following line:
FYI (For Your Info)
The NT Virtual DOS Machine (a.k.a WOW, or Windows on Windows), is a Win16 subsystem that runs under Windows NT, which allows 16-bit applications to run as if they were being executed on a DOS machine, with that machine’s multitasking and segmented memory model.
Because the system is multitasked 16-bit DOS and Windows applications cannot crash NT. However, 16-bit apps within a Win16 subsystem run the exact same way as they do on a DOS/Win 3.x machine; therefore, 16-bit apps within the subsystem can crash one another, or the subsystem. To prevent this, you can launch multiple WOW subsystems as long as your program does not communicate using shared memory.
Windows NT will not allow NTVDM to execute instructions that try to directly manipulate hardware or memory locations. As a result, some DOS and Windows 3.x applications (such as games) may not run under Windows NT.
Windows XP has NO DOS like win95/98 had. Only a dos emulator.
Of course, I mean the dos emulator… not the old MS-DOS or the Win95/98 Dos.
Anyway, you can execute the edit command from command line without to remove that instruction from CONFIG.NT ?
I use Avast Home Edition on Win XP Home Edition too… Maybe it’s a problem of Avast Home version (or XP Home)?
Anyway I’m not the only user that has this problem. Here: http://www.dslreports.com/forum/remark,11186008~mode=flat there is an user with the same problem of mine (and it has resolved it with the removal of that line in CONFIG.NT).
Removing the drive from config.nt will, for sure, remove protection of 16-bit DOS applications. In other words, any virus running DOS under XP won’t be detected. You can test this with eicar.com files and the old pkzip.exe for DOS.
Must found another way to solve the problem.
You’re only by-passing it. Take care
I have tried in many ways, but that error is always there if I don’t remove that line from CONFIG.NT. I hope that a new version of Avast will fix this problem.
