There are so many antivirus programs available in market and it is very difficult to judge for best program to protect your computer. To solve your doubts, companies are offering some day’s trial version for you. You can download the software free from internet and can install it easily on your computer. You can use it for certain number of days and after getting completely satisfied you can upgrade it.
Different companies are providing different trial periods. Companies can provide you with full version or partial version of the software in this trial period. All other versions of software are always available on internet from where you can download them anytime.
There are different ways to extend the trial period of the antivirus software. You can buy a license key which depends on certain kind of application. Many trial software counts the number of days remaining in expiry of trial version and you can also extend the trial period by removing these entries or changing the time in your clock. For .Net based applications you can extend the trial period by again installing the program. Other way to increase the trial period is by changing the date in your computer. You can set the future date while installing the program and then again set the original date. This will really help you to check the software for long time.
There are many people who remove all the registry entries from the program and then install it again after expiration of trial period. They also use some re-setter applications to extend the date and time for unlimited period.
Extending trial version periods like this will able you to use the software for free but you may not get protection against latest viruses. So these processes are only to test the software for little long time. It will really help you to buy the best antivirus software.