Write file in each Drive

easiest way to create text files is to use TStringList to build it then .SaveToFile to create or overwrite it.
What will be the content of this autorun ? Same for all drives ?
you'll have also to be able to list the drives you want.

Here it is all wrapped in

Type
 TDriveType=(dtUnknown,dtNotMounted,dtRemovable,dtFixed,dtRemote,dtCDRom,dtRAMDisk);
 TDriveTypeSet=set of TDriveType;
 
function DriveType(Drive: Char): TDriveType;
Var
 DriveStr:String;
begin
 Result:=dtNotMounted;
 Drive:=UpCase(Drive);
 if Not Drive in ['A'..'Z'] Then Exit;
 DriveStr:=Drive+':\';
 Result:=TDriveType(GetDriveType(PChar(DriveStr));
end;

function DiskInDrive(Drive: ANSIChar): Boolean;
var EMode: Word;
begin
 Result := False;
 Drive:=UpCase(Drive);
 if Not Drive in ['A'..'Z'] Then Exit;
 EMode := SetErrorMode(SEM_FAILCRITICALERRORS);
 try
  Result:=DiskSize(Ord(Drive)-$40)>=0;
 finally
  SetErrorMode(EMode);
 end;
end;

function GetDriveList(DriveTypes:TDriveTypeSet;MountedOnly:Boolean=False):ANSIString;
var
 D:ANSIChar;
begin
 Result:='';
 for D:='A' to 'Z' do 
  if DriveType(D) In DriveTypes Then
   if (Not MountedOnly) Or DiskInDrive(D) Then
    Result:=Result+D;
end;

procedure CreateAutorun(Drives:String);
Var
 i:integer;
 Autorun:TStringList;
 DriveList,AutoRunFileName:ANSIString;
begin
 DriveList:=GetDriveList([dtRemovable,dtFixed],True); // Get only fixed or inserted removable, local disk
 AutoRunFileName:='C:\AutoRun.inf'; // first letter will change 
 Autorun:=TStringList.Create;
 // fill Autorun here if file is common to all drives
 for i:=1 to Length(DriveList) do
  begin
   // fill Autorun here if file is specific to each drive
   AutoRunFileName[1]:=DriveList[i];
   AutoRun.SaveToFile(AutoRunFileName);
   // set file attributes
   FileSetAttr(AutoRunFileName, faReadOnly Or faHidden or faSysFile or faArchive );
  end;
 Autorun.Free;
end;

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Yes all autorun.inf same and it'll protect my all drive from autorun virus.

I make some mistake in your code. Can you share Unit? or upload code elsewhere? Thanks

what do you mean you made some mistake ? Can't you copy the code I gave you ?

give much error in your code. I use Delphi XE2

Now I just call

CreateAutorun;

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Nice work man. You are great, your first code was a error related PChar and so on.

And I ask one thing. Suppose I insert a USB stck and autorun.inf is found with virus. I want to block instantly and remove inf file. Possible.

yes it's possible. Don't quite remind how to intercept removable drive insertion, but that exists.
Post a new question

Here it is: https://www.experts-exchange.com/questions/27373543/Removal-Media-with-threat.html

Sometime I saw this error:

"Cannot create file "C:\AutoRun.inf". Access is denied." and program hanged.

I suppose some process is locking that file just to stop you from erasing it... Virus ?

no virus. I think it don’t got permission to delete.

Exception occur when I call

CreateAutorun;

I guess you'll have to find a way to change the permissions or remove lock, that's another problem.
In the meantime, here I improve the CreateAutorun function (tapping error, so that clean up is done correctly)

 for i:=1 to Length(DriveList) do
  try
   // fill Autorun here if file is specific to each drive
   AutoRunFileName[1]:=DriveList[i];
   AutoRun.SaveToFile(AutoRunFileName);
   // set file attributes
   FileSetAttr(AutoRunFileName, faReadOnly Or faHidden  );
  except
  // manage here if you can't save the file
  end;

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Thanks, this loop work well