16 bit MS-DOS Subsystem error

hi
i have window7,32 bit.recently ,i was having error of fatal error c000021a after pc turned off directly.using boot disk i restored the corrupt "software" file in system32/config folder with a backup.after that pc started fine but i am getting this error "16 bit MS-DOS Subsystem The NTVDM CPU has encountered an illegal instruction." right after logon..i think there are some other corrupt file also.
i have ran chkdsk /r .using google i found out that it is related to Autoexec.nt and Config.nt but i havened dealt with them before. can you guide me to the right direction?

Follow the instructions here

Troubleshooting NTVDM and WOW Startup Errors

Troubleshooting NTVDM and WOW Startup Errors

mithun_mrg said:
Follow the instructions here

Troubleshooting NTVDM and WOW Startup Errors

Troubleshooting NTVDM and WOW Startup Errors

I have been there but is it safe to carry out the said method.i mean if i do something wrong,will it hampers my system?
here is my autoexec.nt autoexec - Pastebin.com
Config.nt REM Windows MS-DOS Startup File REM REM CONFIG.SYS vs CONFIG.NT REM CONFIG.SY - Pastebin.com
also i recently recovered from fatal error c000021a.

increase the files count to 250 in ur config.nt & see

also add this line without quotes

"shell=%SystemRoot%\System32\Command.com /e:4096"

& to add always take a backup of ur sensitive data before doing anything because modifying registry or system files carry certain risks & don't blame me on any member if something going wrong

mithun_mrg said:
increase the files count to 250 in ur config.nt & see

also add this line without quotes

"shell=%SystemRoot%\System32\Command.com /e:4096"

& to add always take a backup of ur sensitive data before doing anything because modifying registry or system files carry certain risks & don't blame me on any member if something going wrong

tried , but still getting errors.how to i extract a specific file from window7 disc and replace the file on my system if corrupted.

then first try sfc/scanow at command prompt if that fails to resolve ur problem then use this guide to extract & replace the corrupted file
Extract Files from Windows 7 Installation DVD - Windows 7 Forums

can anybody tell me what are the specific files that are related to this errors?
i tried changing himem.sys but still error occurs.

^^have u changed it from "sysedit"

mithun_mrg said:
^^have u changed it from "sysedit"

sorry for using wrong word ,i don't changed but replaced it with a backup file from winsxs folder.
also using sysedit give error "
---------------------------
System Error
---------------------------
The Win16 Subsystem was unable to enter Protected Mode, DOSX.EXE must be in your AUTOEXEC.NT and present in your PATH.
---------------------------
Close
---------------------------"

please elaborate how did u open sysedit

mithun_mrg said:
please elaborate how did u open sysedit

i tried to run sysedit by using "run" and giving sysedit command in elevated command prompt .both return the previous error.

go to folder options select show hidden files & uncheck the option hide protected os files
go to c: open the file config in notepad add these lines & reboot
dos=high, umb
device=%SystemRoot%\system32\himem.sys
files=20

if these fails try running this command from run
cmd /c copy /y %windir%\repair\autoexec.nt %windir%\system32

try these & get back

What i think is that some startup program has gone corrupted.Use Ccleaner and try disabling unwanted startup entries.

mithun_mrg said:
go to folder options select show hidden files & uncheck the option hide protected os files
go to c: open the file config in notepad add these lines & reboot
dos=high, umb
device=%SystemRoot%\system32\himem.sys
files=20

if these fails try running this command from run
cmd /c copy /y %windir%\repair\autoexec.nt %windir%\system32

try these & get back

tried both of them but still getting errors but i have found that at login when i get this error ,ntvdm.exe running .
using process explorer(sysinternals) i got this

image file- ntvdm.exe version-6.1.7600.16385
path-c:\windows\system32\ntvdm.exe
command line-c:\windows\system32\ntvdm.exe -i 1
current directory-f:\program files\startdock\object desktop\deskscapes\
parent - <non-existent process>(2644)

i am using stardock fences on my desktop but i am not using deskscapes right now.

disable all start up items from msconfig & see the same error pops or not

mithun_mrg said:
disable all start up items from msconfig & see the same error pops or not

i have only comodo internet security as startup and disbling it does not affect the error.

then the last option for u is system restore

sorry for late reply as i was oflline.BTW here is a screenshot of the error
*i54.tinypic.com/24w5x02.png
i used the sfc command but still the error as usual.and now after doing sfc my system just freeze up while doing anything .its not specific to any program or time.even task manager don't come up by ctrl+alt+del.
pc don't don't respond to any keypressses.usually num lock indicator was the indicator of pc hanging for me but it is normal.