We're going to need some more info before we can properly address your problem. Tell us the year and model of your MacBook Pro and which version of OS X it's running. And what have you already tried in order to resolve the freezing and distortion?
Model Name: MacBook Pro
Model Identifier: MacBookPro2,2
Processor Name: Intel Core 2 Duo
Processor Speed: 2.33 GHz
Number Of Processors: 1
Total Number Of Cores: 2
L2 Cache: 4 MB
Memory: 3 GB
Bus Speed: 667 MHz
Boot ROM Version: MBP22.00A5.B07
SMC Version (system): 1.12f5
OK, thanks for posting the specs. According to my Mactracker, your MacBook Pro is a 15" 2007 model using an ATI graphics card. We need to first check your hard drive to see if that's the cause of the freezing. Do you still have your original DVD that came with your MacBook Pro when you purchased it?
OK, I guess we have to do the check by a different means. Please read the following Apple KB article and follow directions to do a "fsck" check on the hard drive. Copy the instructions and then print them out so you can follow them easily.
I hate to say it, but that MB Pro's ATI graphics card may just be finally failing. Most gave up long ago.
I have the same model that was repaired on Apple's extended repair program, long expired, to address the display problem with those models. But the MBPro wouldn't even boot, just dead with a black screen.
I hope not, but just a forewarning in case software fixes don't work. ;(
And have you tried booting up into Safe Boot Mode and see if things improve?