XP cannot start new processes when PID tends to 65000?

I run XP Home SP2 on a Pentium 3,2 GHz with hyperthreading.

When I start the following program .\test.bat in a DOS-like window

("Eingabeaufforderung" in German)

@echo off

set c=1

:loop

cmd /c echo > nul

echo %c%

set /a c=%c%+1

if %c%==123456 goto end

goto loop

:end

all works fine, but after a while (sometimes c~30000, sometimes 15000,

depending on what other processes are running)

I get an error message for each echoed number (probably from the line

beginning with command):

"Das angegebene Programm kann nicht ausgeführt werden"

what means s.th. like

"the program cannot be executed"

If I finish and restart test.bat, it sometimes works for the first few

numbers, but soon the error messages return. This is also true

if I close the DOS-like window and reopen it or even if I log out

and log in again. Only a reboot works.

In this state I also cannot start other new processes like browsers

or editors. Closing another running application sometimes allows

to open s.th. like wordpad, but when opening a second instance of

wordpad the system gives an unspecific error message (in English

s.th. like "error while creating an empty document"). Even the

shutdown process hangs sometimes and I have to power off

as a last resort.

The problem also appears when I'm running cygwin on large file trees

with a command like

find mylargefiletree -type f -exec grep mysearchword {} \;

The error message occurring after some time then reads "cannot fork",

which obviously means

that no new grep processes can be started.

I watched the problem with the taskmanager (tabs system resources

and processes, all possible columns visible) and with procexp, and it

seems that the

problem are the high PIDs: It always finishes when process IDs

about 64000 or 650000 are reached.

Memory issues don't seem to play a role, it happens with disabled

virtual memory and with a fixed length memory file, and the task manager

shows, that in the latter case the virtual memory is not exhausted yet.

Also the number of running processes is not too high.

Did anyone else here register this problem? Are there any workarounds

for this? (The test.bat may not be very useful, but I would like to run

the cygwin example from above.)

Thank you in advance

Bernd