If you were complaining that when you print a page from inside Internet Explorer and the right edge of the window is cut off, I would tell you to adjust your browser printer margin settings. For example, in Microsoft Explorer select File menu, then Page Setup and reduce your left and right margins to 0.25 inches.
You said this right-side-truncation occurs when your DOS program prints. It used to be okay, so what changed? If it is a new printer, check its default print settings. If it isn't new, did someone change those settings? (A DOS program does not use the Windows printer installed drivers.)
The reply above by kiddpete suggested one way for you to print from a DOS program in newer computers, so I'll add a comment too that you can consider. For example, soon many new printers will be connected with USB. Well, DOS has no way to write directly to USB printers. Solution (really a workaround): There's a program named PrintFile that you can install that monitors a directory of your choice and any files you write or copy into that directory are printed then deleted by this Windows program. Real Neat. Check it out.
thread182-155776 - about PrintFile program
thread182-66171 - a way to speed up printing