How to open my PDF ebook

I bought two ebooks (pdf) from Amazon 2.5 years ago. Initially I think I could open these two books with Adobe acrobat 5. I did not touch these two books in the past two years.

recently I tried to open these two books with my new computer and with Adobe reader 7. Now Adobe reader does not allow me to read the ebooks, prompting me to reactivate from both the new computer and original computer with which the downloading was conducted.

My original computer has long been gone. This makes my ebooks useless. I would appreciate all advice/help on how to read the ebooks. Even if I could open them once, I would just print them in hardcopy.

M Ma