Macbook Pro 13-inch (10.6.8) random white/black screens and becomes unresponsive...what is wrong/what to do to solve?

Question

PLEASE PLEASE READ THIS I'M IN NEED OF URGENT HELP. || Heeey everyone! I'm new here. Please don't bite me. =))
Okay. So I have a Macbook Pro, 13 inch (bought Dec. 2010). It's currently running on Snow Leopard (10.6.8). It had a hard drive crash in Feb. 2012...I had it replaced and lost all my files . It had two major falls (January 2011 & November 2012). Oh, and it also makes this weird grinding noise when you listen closely.
Everything was going fine, until last week, I encountered a kernel panic. Restarted, but was faced with that awkward blank white screen thing at start up. I was told at the Apple Store back when my hard drive crashed in Feb. 2012 that repeated pressing down of the power button can be damaging, so I waited for it to run out of battery to restart. After that, it was normal again. I downloaded OnyX and verified/repaired permissions...nothing was out of the ordinary.
THEN. The next day, in the middle of use, my mac suddenly black-screened. Not a lot of windows were open, and I wasn't doing anything that...will put a strain on anything. It wasn't total pitch-black like the screen looks like when it's turned off. I could still hear the hard drive working and making that grinding sound. I pressed the caps-lock key, and it didn't light up. =))) What, is it off or something? But I can still hear the hard drive there. And it's totally unresponsive. So I decided to restart by pressing down the power button. It was normal again...until a few hours later when it suddenly white-screened. OKAY it's white now. I don't know what that's supposed to mean. But it had the same symptoms as the black-screen. Unresponsive, caps-lock didn't light up, normal grinding sound as if the computer was still on. So I let it run out of battery so I could restart. Upon restarting, I opened Disk Utility and verified disk permissions. There was no damage, nothing again.
I recently got uTorrent (around late December), and thought that it might have been that, so I deleted it and emptied trash. The next day, it did the black screen again. Same with the next day. There's at least one per day. It didn't seem to affect performance at all, everything still ran smoothly. I made sure to check disk permissions to see if everything was okay. And everything was.
Then, about three days passed without any black/white screen and I thought that nuisance was over. BUT NO. Two days ago, I got black-white-white screened and I was...shocked. I let it run out of battery again. =))) Checked Disk Utility, again, nothing. So I decided to get that Software Update thingo that always pops up. I upgraded to 10.6.8. A day passed without the dreaded black/white screens. But yesterday, it white screened once. And today, it white screened again.
I really can't figure out a concrete pattern. It seems random. But what I do know is that:
1. It happens in the afternoon. All the time, consistently in the afternoon. LOOOL IDK what this is supposed to mean, but its one of the common factors. =))
2. Most of the time, it happens when I leave the computer for about 30 seconds - 1 minute to get something. Or if I'm watching a long video (like a TV show episode), a period of time where I don't touch the mouse/press any keys. Is that related somehow?
3. I can't do anything to get it out of the white/black screen except restart. Each time I restart, I check Disk Utility and nothing is wrong.
And yes, I've went to the Apple Store to get this checked. All they said is: "Upgrade to Lion, maybe the error will disappear. If it does, then it was just a software error. If it doesn't...then sorry." LOOOOOOL NOT FALLING FOR THAT, not spending money when I'm not sure it'll fix the error. I want concrete answers.
I'm a student, and my Christmas Break will be over in less than a week. SO I NEED ALL THE HELP IN THE WORLD PLEASE. What is wrong with my laptop? Can I fix this? Will opening it in safe mode help in any way? PLEASE I'M DESPERATE.

Answer 1

Try these:
See what's loading in your login items. - delete the ones you don't need.
Open up Activity Monitor and under all processes, see what's using most of your cpu's resources.  Highlight the ones using the most % CPU and hit quit process.
Next, open up disk utility and verify your disk.  Once that's done, verify disk permissions - repair if needed.
Restart your Macbook and see if it speeds things up for you.
good luck....