IMac Previous Owner Password Problem

I just received an Imac from an estate. I'm new to this computer and pretty much a dummy with MACs. It's a newer model purchased Jan 2010.
I cannot install IWork because the install script requires a password, which belongs to the previous owner (deceased). Can I get around this, can I change ownership to my name and password?

Thanks in advance.

The best way to achieve this is to purchase an installation disc and do an "Erase and Install" of the operating system.

Is MAC OS that restrictive...?

It's really not so much a matter of restrictiveness but a matter of prudence. You have no idea what is installed on this Mac. It could possibly contain malware, harmful files, or a faulty operating system, etc. By purchasing the installation disc and performing an "erase and install" of the operating system, there would be nothing to worry about.