That's a very large question, so perhaps you can provide more details to
help focus in on a possible reason, and more importantly, some possible
solutions.
First, what have you tried so far?
Second, what were the results of those trials?
In answering those questions, it would also be useful to include details
like the media (DVD's, downloaded file, etc.) from which you are attempting
to install the application. Do you own a valid license for this particular
application? If not, why not? Also, what type of PC you are attempting to
install it to, what operating system is installed on it, etc.
Best of luck to you.
