Similar problem in both real and protected mode, and in TurboVision programs too
(but the error number may be 19 instead of 150).

This problem occured on every hardware I have tried (486, P133, P200MMX, Celeron
266, P II 350).
Problem occured under MSDOS 6.20, 6.22, PCDOS 6.3 and Windows 95/98 when booted
in dos-only mode; did not occur under Windows NT 4.0 nor on Windows 95/98 when
booted GUI.

There may be a problem in the standard Pascal's INT24 handler (maybe the DOS 54H
function call isn't enough to "get DOS into a stable state"?) or in other part
of the RTL. There may be a correction in BP 7.01 but I only have BP 7.0  - could
you try it?

Source enclosed. Steps to demonstrate the problem:
  1. Assure that the program will be able to create, write and delete
     a temporary file c:\$$$.$$$ (or change the TempFName constant).
  2. Compile the program (for real mode).
  3. Prepare a diskette with a non-empty file 'TRY.TRY' in root directory.
     Notice that the file MUST not be empty - otherwise the problem does
     not occur, at least at me.
  4. Boot clean DOS (press F5 to bypass CONFIG.SYS and AUTOEXEC.BAT).
     (You can experiment with different configurations too;
      if you run Windows 95/98, try when restarted in DOS-only mode.)
  5. Write-protect the diskette and insert it into drive a:
  6. Run the program.
     You get this output:
     erase a:\... error 150;
     if you get some additional error 150 message (I get it regularly),
     the problem occured.

I would appreciate any message (tell me your compiler version, OS, and if the
problem occured).

{ **************************************************************** }
program Try;

{ Program to demonstrate Borland Pascal 7.00/MSDOS error (?):
  after error 150 (disk is write protected), some next operation fails
  with error 150 again. }

{$i-}
const
  TryFName = 'a:\TRY.TRY';  { name of existing non-empty file on write-protected
disk }
  TempFName = 'c:\$$$.$$$'; { name for temporary file that program can create }

var
  f: file;
  er: Integer;
  i: Integer;
begin
  { try to write to write-protected disk }
  assign (f, TryFName);
  erase (f); er := IOResult;
  writeln ('Erase ',TryFName,': error ',er);

IOResult:=0;

All this happens on undocumented ground and due to informations of
probably Schulman's book Undocumented DOS. After a lot of expirmenting
I've still not found a foolproof way to avoid the terrible "delayed"
error messages - which may occur once or even twice at the command
line _after_ the TP program terminated (!), except by shutting up TP's
handler:

var p:pointer;
procedure myint24;assembler;
asm
  mov ax,3
  iret
end;

...
begin
  getintvec($24,p);setintvec($24,@myint24);
  ....
  setintvec($24,p);

around sequences accessing floppies. This handler will return to DOS
with the message FAIL which will tell DOS to terminate the offending
DOS function with a (possibly obscure) error code. There is a slight
risk, though, that DOS may decide that it cannot terminate reasonably
the offending function and terminates the program instead via INT_$4C.
But I've not yet seen such a case.

In your case (erase file on write-protected disk) the IOResult
returned now will be 2 (file not found) which is not so bad after all.

Jay
--

program Try;

{ Program to demonstrate Borland Pascal 7.00/MSDOS error (?):
  after error 150 (disk is write protected), some next operation fails
  with error 150 again. }

{$i-}
const
  TryFName = 'a:\TRY.TRY';  { name of existing non-empty file on
write-protected
disk }
  TempFName = 'c:\$$$.$$$'; { name for temporary file that program can
create }

var
  f: file;
  er: Integer;
  i: Integer;
begin
  { try to write to write-protected disk }
  assign (f, TryFName);
  erase (f); er := IOResult;
  writeln ('Erase ',TryFName,': error ',er);