dos prompt does not work

I have laptop with xp home on it
it was having a virus backdoor .sdbot
i run stinger it deleted some files
after that in command prompt
it takes some os command
but commandlike edit also not working it gives
error c:\windows\system32\autoexec.nt the file is suitable for running msdos
& it shows 2 dialog box close & ignoire
i had tried both nothing happens
pl help me assp
thank in advance