|Depends on why it does it. Some virus's and other software issues can cause it. Many hardware issues can cause it.|
Get a ultimate boot cd and try to run memtest maybe first.
As long as your hard drive is OK you will end up being able to get data off by some means. Just don't format or do repairs just yet.
1/3 of highway deaths are caused by drunks. The rest are by people who can't drive any better than a drunk.