The old school method would be to write the invoice out as a text file and then use a shell/system command like "type invoice.txt > prn".
I have no clue if PRN still works under WinXP, but it wouldn't take too much effort for you to try.
1. create a small batch file with the type command.
2. write the invoice to a text file
3. EXECUTE FILE my_batch_file.bat
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TAZ
BTW, your message title is annoying and I was tempted not to reply. Get a clue about the culture of this forum and use meaningful titles with a minimum of repeating characters and exclaimation points.