These days there is absolutely no excuse for not being disorganised! Gone are the days of having to rely on a piece of pen and paper to remember birthdays and to-do lists. Now you have help from software and the internet to make sure that you do not forget anything, from your anniversary, to http://www.organiclocalnumbers.co.uk to your best friend's birthday.
If you are going to rely on software to manage your time and your life, you need to consider several things. It is better if you decide on your personal organisation strategy up front and start from scratch then if you pick several different methods to organise different aspects of your life, as you will find it difficult to integrate them later.
Portability is one thing you should consider. If you install time management software on your PC you need to make sure that you can access it from other computers and in other countries too, so a web based software is a good option.
Second, are you willing to pay for it? There are some very good free organisational programmes out there but you may get additional features if you buy software dedicated for it.
Many smart phones do come with calendars and contacts lists which can usually be synchronised with your PC – this can be a good option although the capabilities are often more limited.