Oh my mistake.
Not the baudrate is the problem (is only 9.600).
The time to send or recive a telegram is the problem
(Telegramm lnength:64 -> XP-time: 1.1s -- DOS-/Win98-time: 0.2s!!)
The program "DosBox" (freeware
http://sourceforge.net/projects/dosbox/)
handels the com-port is handelt well
but not the clock (after 23:59:59 > 24:00:00 >> 24:01:00 ...)
"Kithara »DOS Enabler«" (ca 180,- EUR/PC
http://www.kithara.de/) handels both.
Is ther a way with "windows-onbord-metods"?