That error means its having difficult finding your operating system (Windows). Possible hard drive failure, possibly just the OS being corrupt.
If you don't have a Windows 7 disc to reinstall, you may be forced to do a restore. Keep in mind that a restore will wipe out all your personal files on the computer though.
If you're ok with that, I can help you find the restore partition on the drive if the drive is functionaly. (which is what is likely where the restore info is if you didn't get a restore CD with it). (Normally for Toshiba its F12)