MacBook – My macbook pro hard drive seems to be corrupted, should I replace it

I have a 2,26GHz mid-2009 macbook pro with 8Gb Ram and mountain lion (mac os x 10.8.2). Recently my computer doesn' t stop freezing and I have to force the computer to shut down. Then I cannot boot at all the computer shows a flashing folder with a question mark. When I run disk utility from the installation cd then I am able to boot from the drive again but it will eventually starts lagging after a few minutes of utilization with software's such as safari, skype or even the finder. I wanted to get a ssd recently. Will it fix this issue or the problem might lie elsewhere? I tried to boot from different sessions it always freezes at a moment, I have been able to run a virus scan disk and I didn't find any virus nor trojans .