Switched from Mac to W7 and need advice

Recently I decided that I'm fed up from Mac osx and I've decided to go to pc for various sorts of reasons. But I'm an idiot with Microsoft so I want some advice,

1. The last time I have a pc was 6 years ago, it was running windows XP, and it used to crash ALLL THE TIME and was super sloww. Are pcs still that crush prone is slo? And please be honest.

2. My dad, Mac lover, told me that the old pc he had was always getting viruses. My mom said the same. Will I always be get viruses, and if I do, what are good anti-viruses that will get rid of them.

3. The pc I want to get is a Lenovo idea pad z570 and I want to know if it's any good, specs are : i5 2.5 ghz processor, 4 (going to upgrade to 6 or 8) gb ram, 750 hard, and intel hd3000 graphics. Basically going to watch YouTube, movies, web browsing, microsoft office things, and some very little gaming. (command and conquer generals, that stuff... Don't judge lol)

Thanks a lot and I just want your advice from some guys who know what there talking about thanks for your advice!