Short bio: Computer Scientist, FOSS supporter (read more)
Tux Machines (TM)-specific
You might be wondering why I am suggesting an Linux distro for your mom. Well Linux is no longer the stronghold of geeks. Distros like Ubuntu have made using Linux as simple as using Windows. Here are reasons why Ubuntu will be perfect for your mom, who's needs are basic.
The reasons are:
1. Ubuntu is one of the easiest OS to master: Your mom will be soon at ease with the new environment.
2. Security: With Windows there is always the constant threat of viruses, Trojans and malware. This coupled with the fact that online transaction is a daily necessity, if users are not careful hackers may get access to sensitive information like bank passwords. With Linux there is almost '0' threat of any virus related problem.