You may not need a brand new laptop yet, however you probably need to do some major work on that one to keep it functional. Its not a bad laptop by any means, and it should be able to serve you for about another 3 years.
But the mouse button not working and the battery dying are not good signs. It usually seems that when a laptop starts to break down they are on their last legs. There may be things we can help you do to slow its decline into the grave.
- If you decide that you dont want to mess with fixing your Compaq then we can help recommend a new computer in your price range with the features you desire.
Have you ever had the inside/outside of the laptop cleaned, to remove all the dirt and gunk? If you have never done this, then do it yourself or consider taking it to a small local computer store to get it cleaned.
If you are using the mouse keys on the laptop, dont anymore. Instead get an external, wireless mouse.
As for it starting slow, it could be hardware and/or software problems. We can help you out with that stuff (diagnostics, software cleanup, etc...).
First, get that laptop clean. If its dirty and it cant cool the parts effectively, that may be a BIG part of why its running slow and freezing.