I have a white 13" MacBook from about 2008. And recently my computer has been saying my hard drive is full. When I start up my computer it says I have about 2.0GB free space left, but as I use it the space available goes down and down til there isn't enough for me to run Firefox. And if I restart all the space is back.
And about once a day I get the grey screen that says my computer needs to be restarted (in about 10 different languages). I used to only get this when my external hard drive was accidentally disconnected.

Are these problems fixable or should I just get a new computer.