Hello I have a Sony Vaio desktop RUNNING on wIndows vIsta pc Model PCG-2J1L and I recently had an issue with it starting. It froze and I restarted it and overtime I turn it on it takes me to the screen that asks to launch startup repair or start normally . When I start normally it restarts and takes me to the same screen when I launch the startup repair it LOADS then takes me to a black screen with an arrow . I tried PRESSING F10 to go to recovery center to reset my computer when I turn it on but it loads and takes me to the black screen with the arrow again I've tried booting at last successful boot but it takes me to a black screen that says operating system not found. Please help me , your help will greatly be appreciated . Thanks .Probably the most common CAUSE of the "Operating system not found" message is a damaged or defective hard disk. There are a set of troubleshooting steps here:

http://support.microsoft.com/kb/321626

You can work through the guidance on that page but be aware that a trip to a repair company or shop MAY be necessary.