echo Hello, > file.txt
echo. >>file.txt
echo world >>file.txt
and you can always run:
wordpad file.txt
on any version of Windows.
On Windows 2000 and above you can do:
( echo Hello, & echo. & echo world ) > file.txt
Another way of showing a message for a small amount of text is to create file.vbs containing:
Msgbox "Hello," & vbCrLf & vbCrLf & "world", 0, "Message"
Call it with
cscript /nologo file.vbs
Or use wscript if you don’t need it to wait until they click OK.
The problem with the message you’re writing is that the vertical bar (|) is the “pipe” operator. You’ll need to escape it by using ^| instead of |.
P.S. it’s spelled Pwned.