If you have ever downloaded a demo or a program that has a 'trail period' and has run out, theres a simple and easy way to keep using that product without uninstalling and re-installing (that method only works occasionally).
Firstly all you have to do is change the date of your computer back 1 year. Simple and easy. The trail or demo will continue to work.
However, sometimes it will mess up your calender etc, but is very simple and easy trick!