Help: scanning old computer manuals

Ok, I've finally gotten around to attempting to scan a lot of the classic computer documentation that I have. However, I have run into a problem perhaps some here could shed some light on... Whenever I scan a page from a manual, the scanned image on the screen looks horrible. However, when I print it out it is absolutely perfect. Yes, I've tried zooming in on the image on screen, it is unreadable still. One more twist is that if I send the image to my OCR software, it turns it into text with almost perfect accuracy. My scan settings are Line Art at 300dpi. My scanner is legal size, a scanport 2400 and the application software is Uload Photoimpact SE. My printer is an HP deskjet 820cse, and the video card in my system is a Diamond speedstar A50 w/8mb ram. Since the scanned document looks bad even when still in the scanmodule driver (before getting passed to the graphics application), I don't think photoimpact has anything to do with it. I wanted to put some of the scanned documents up on the web, but since they look horrible on screen I'm not sure how to proceed. Of course, they can be downloaded and printed and look great, but... I have downloaded old dec documentation that looked fine onscreen and printed fine too. Any suggestions? What am I doing wrong? Jay West