Currently Being ModeratedFeb 25, 2013 9:34 PM (in response to maureenyo)
Try restarting your system with the original system disk that came with your computer then, run disk utility to verify/repair your hard drive.Take a look at this link, http://support.apple.com/kb/HT1782
Currently Being ModeratedFeb 25, 2013 9:38 PM (in response to maureenyo)
If Eric's suggestion does not work and you do indeed have a hardware issue, Apple will not repair it since it is now old enough to be considered vintage. I was lucky enough to get my '06 MacBook repaired just a month or so before they attained their vintage status, and with the 90-day repair warranty, I actually had a vintage machine tht still had warranty.
Currently Being ModeratedFeb 26, 2013 9:22 AM (in response to maureenyo)
You might want to restart while holding the shift key down to enter safe mode. It can check and repair the file errors for some problems.