pc questions need to be solved

ASAP
首先我要說明的是我是一個電腦白癡， 所以懇求各位賢人能士能夠多多諒解我的無
知並且回答一下我的問題。 感激不盡啦。

If I want to watch movies from desktop, what kind of software I need to install?

If I want to make sure my pc is not being infected from all those kinds of viruses, what kind of super stuffs I need to have in the PC?

If I want to make sure my memory is big enough for thousands personal photoes, what shoud I do?

我好羅嗦噢！！！！！！！！！！！！！！！！！ 不好意思。 拜托了