Huge "no" sign when I start up my Macbook...

[lnfinity]

I'm kind of tired of my Macbook messing up. It's already had so many problems with starting up. Anyway, enough of that.

Lately, it's been really weird and really laggy at times. Sometimes the internet will stop working although the wifi is perfectly fine and the internet works on my other laptops. And the only way to fix that is to restart my laptop. Well, it happened again, and now it isn't letting me start it up fully. I'll turn it on, and it'll play the start up sound and show the light gray background with the gray apple, but then the apple turns into a "no" sign like this . As I'm typing this, the "no" sign is now gone and it's just the light grey background. The fan is really loud too.

I hope this isn't a huge issue... I don't want to get a new harddrive again I'm so stupid, I never backup my files. If you guys have any tips, that'd be awesome! Just to warn you, I'm REALLY dumb with technology so please use common English when explaining.

 

[simsaladimbamba]

Have you tried any of these steps?

Mac doesn't boot

Resolve startup issues and perform disk maintenance with Disk Utility and fsck

Troubleshooting: My computer won't turn on

A flashing question mark appears when you start your Mac​

 

[156457]

Hold down the Alt/Option key when you boot the computer (before the Apple logo shows)... are any hard drives listed?

 

[lnfinity]

Omg thanks for the fast replies you guys! <3 I looked at one of the links (the MacRumours Guide one) and it seems that it might be a failed software update since I just recently skipped the latest software update... but I tried the SMC reset, PRAM reset, and safe boot and none of them have worked so far. And when I press the Opt key when I boot, my hard drive is listed, but the same problem happens after I press enter to select it.

Edit -
OMG! Safe boot worked you guys! Thank you so much! <3 But there's still another problem... it's been lagging if I do certain things on the internet pretty badly, where I have to wait sometimes even 5 minutes for it to come back after being frozen. And sometimes the internet will stop only on my Macbook and I can't get it back until I restart my laptop.