pc questions need to be solved

ASAP
首先我要说明的是我是一个电脑白痴， 所以恳求各位贤人能士能够多多谅解我的无
知并且回答一下我的问题。 感激不尽啦。

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?

我好罗嗦噢！！！！！！！！！！！！！！！！！ 不好意思。 拜托了