I have SONY VAIO with windows 7 pre installed. I have installed the UBUNTU in other partition to work as dual boot. I am trying now to restore the factory settings with ALT + F10 which is not working any more. Each time its giving me screen to choose operating system. How do I restore my system now?
I assume you want to delete Ubuntu and restore Windows to original state (factory settings)?
Note that I'm not familiar with Vaio, however on boot screen (grub) you should be able to see installed systems. For Windows you should have more than one entry and the first one
sda/dev1 (or similar most likely) is rescue partition of Windows. Boot there and follow to guide to re-install Windows.
Hope it solve your problem.
I'm not familiar with Vaio in particular, but these days most computers come with a hidden 'rescue' partition that's used to 'restore factory settings'. That it doesn't work for you could indicate that you have deleted this partition (perhaps when installing Ubuntu).
Take a look at the partition table (eg. with gparted) and check if there's an extra partition you don't use; it'll probably be 10-20 GiB in size, and may be hidden, labeled 'Rescue' or somesuch, and formatted with either NTFS or FAT. If it's there, try editing your grub configuration to show it as a boot option from the menu -- perhaps it's just that the BIOS is confused by the partition layout, but if you boot it directly it'll work fine.
If it isn't there, then the only way to reimage the system ('restore to factory settings') is to use an external rescue media you probably could have made on first Windows boot. If you don't have it, I'm afraid you need to contact Sony tech support.
You should go through answers of question How to remove Ubuntu and put Windows back on? before proceeding. I believe you will be redirected to the correct way to do it after referring to this question.