Freezing/ Error code M1004 HELP!!

  I have an Inspiron 1505 about five years old.  Lately my computer has been freezing and shutting down for no reason.  I can be just reading and it'll freeze.  This isn't the first time it has been happening.  Back in April I had the same problem. The error message indicated that my hard drive was going bad so it was replaced.  Now it's doing it again.  This time I got error code M1004.  From what I read, this is something about heating.  What I have noticed is that the bottom of my laptop runs extremely hot.  Will getting a cooling pad help?   Any ideas will be useful.  Thanks.