Entropy causes hard disks to go bad.
When it freezes, can you hear repetitive motion from the disk, a result of seeking the same area repeatedly? That could be a sign of impending failure.
Hard disks are not terribly difficult to replace.
If the cursor itself cannot be made to move at all, it's a different manifestation of entropy.
General purpose Mac troubleshooting guide: Isolating issues in Mac OS X
Creating a temporary user to isolate user-specific problems: Isolating an issue by using another user account
Identifying resource hogs and other tips: Runaway applications can shorten battery runtime
Starting the computer in "safe mode": Mac OS X: What is Safe Boot, Safe Mode?
To identify potential hardware problems: Apple Hardware Test
No I cannot hear it. Actually it's a recently replaced disk. Shouldn't have any problems. Maybe it's actually my ISP becuase it always occurs when on the net. Ran disk utility seemed fine. Thought it may be my USB disk that is connected that sometimes is searched that would slow it down, but its not, becuase I disconnected it and it still happens if not less often...
Actually i've found this happened on allot of old macs I used to own.
Dunno what it could be.