According to the US Copyright Office website:

As a general rule, for works created after January 1, 1978, copyright protection lasts for the life of the author plus an additional 70 years.

Click to expand...

So yes, these works are still in copyright. Though the books are 20 years old and for a software product that is no longer sold or supported. Software manuals tend to be rare, infact, google searching "think pascal manual" and this topic comes up as #2. Google books has a spot for the book, but even they do not have so much as a cover or snippet to view. I don't think Symantec will be upset for preserving them. (Though if this goes against forum rules an admin/mod can remove all links to the content.)