OS X 10.6.8 keeps freezing on my 2008 Macbook Pro

Question

I recently upgraded to OS X Snow Leopard and every now and then, maybe up to twice a day, my macbook pro freezes. While using the computer regulary for anything, at randomly the entire screen will blink and freeze at whatever I was on, and only the mouse cursorer moves and I cant do anything at all. The only thing to do is to force shutdown. I check the disk using the disk repair utility and it says everything is fine. Prior to this I had upgraded to Snow as well and the same thing kept happening, and eventually one day led up to my mac not booting up, forcing a reisntall as of yesterday. Why is this happening and what can I do to prevent this from happening again?

Answer 1

Third-party system modifications are a common cause of instability and poor performance. The following procedure will help identify which such modifications you've installed. Don’t be alarmed by the complexity of these instructions -- they’re easy to carry out and won’t change anything on your Mac.
Launch the Terminal application, copy or drag -- do not type -- the line of text below into the window, and press return:
kextstat -kl | awk ' !/apple/ { print $6 $7 } '
Post the lines of output (if any) that appear below what you just entered (the text, please, not a screenshot.)
Next, do the same thing with this line:
sudo launchctl list | sed 1d | awk ' !/0x|apple|com\.vix|edu\.|org\./ { print $3 } '
That's one line, not two. You'll be prompted for your login password, which won't be displayed when you type it. You may get a one-time warning not to screw up. You don't need to post the warning.
Next, this command:
launchctl list | sed 1d | awk ' !/0x|apple|edu\.|org\./ { print $3 } '
Again, one line. Finally, one more:
ls -1A {,/}Library/{Ad,Compon,Ex,Fram,In,La,Mail/B,P*P,Priv,Qu,Scripti,Se,Sta}* 2> /dev/null
Remember, this is all drag-and-drop or copy-and-paste, whichever you prefer -- no typing, except your password.
You can then quit Terminal.