Q: My Mac freezes up all the time and its really slow

I bought my Mac OS X Lion 10.7.5 in August 2011 and it was working great. bu for the last year or so its been really slow.  it also freezes up and the only way to get it to work again is to force close the program that freezes up or i have to go as far as to turn of the machine.

in the beginning it was just freezing when i was working in photoshop, but now it happends to all of the programs on my mac, especially firefox. and its really becoming a big problem because i can't do anything without risking it to freeze up and i loose everything i have done/worked on.

and its also very slow. things that should take a few seconds to do, takes several minutes to get done. i need this mac for work and my studies, so as i said its a real problem when it wont work.

it dosent help restarting the mac. done that a thousand times and its just as bad when i start it up again.

anyone who knows how to fix this?   i really hope some of you can help me!