MBP frezzes up - constantly

More information is needed to help you to a fuller extent.

What MacBook Pro (when did you buy it) and what Mac OS X version do you use, http://docs.info.apple.com/article.html?path=Mac/10.5/en/8473.html
have you installed anything recently,
how many minutes/hours does it take until the freezing sets in?

What is the clock speed of the CPU (x.y GHz),
how much RAM do you have installed (z GB),
do you have enough free space left on you HDD (10-20% of its capacity, 43-86GB on a 500GB labeled drive for example)?

Have you tried repairing permissions via Disk Utility or the installation DVDs yet? http://kb.wisc.edu/helpdesk/page.php?id=3810

Have you tried resetting the SMC or PRAM yet? http://support.apple.com/kb/HT1411 http://support.apple.com/kb/HT1379

Have you taken a look at Activity monitor, what process might hog up the CPU (Show All Processes and sort by CPU usage)? http://www.ehow.com/about_5374100_activity-monitor-explained.html

 

If you're running the 1.7 firmware with a third-party HDD, join the party. Here's 122 page of complaints:

http://discussions.apple.com/thread.jspa?threadID=2054387&start=0&tstart=0

Apple doesn't seem to want to do anything about it either...

 

If you can, watch again, when the computer freezes again. Also have a look at the disk activity and see if there are spikes like 30-60MB/s.



You can also use iStat Menus to do that. www.islayer.com

 

Yep, it has to do with the hard drive. In the 13'' MBP 7200rpm drives don't play nice.

 

If you're running a June '09 MacBook Pro (15" or 13") and you don't see anymore "updated" under the Software Update utility, you're more than likely running firmware 1.7.

SATA II HDDs and SSDs don't play nicely at all in most of these notebooks. There's definitely a problem going on.

That being said, if your stock drive is working and the third-party one isn't, you're in the same boat as the rest of us and Apple really doesn't give a **** unfortunately