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The last laptop I encountered with that problem had a damaged MBR (Master Boot Record). I had to boot the computer using a Windows XP CD, in the installation menu, I choose R for repair console, then in the console I ran the "FixMBR" command.
Because this is a netbook (no CD/DVD drive), you would need a USB DVD drive, and a XP CD (presuming that you are using XP on the computer). Otherwise there are many online walkthroughs on creating a USB Bootable drive for loading the repair console (they are of varying degrees of difficulties, so I won't post them, but you can find them by doing a google search for "windows repair console USB").