how can i reboot my netbook?

You reboot your notebook every time you turn it on.
You should have a reset button somewhere.

This error appen when you have a non-system boot drive. The wording is a legacy from the old DOS days when computers where floppy based without hard drives. It mean that your OS installation got corrupted by the suppression of a key system file. Another possibility would be a faulty/dead main drive.

If you have a CD or DVD drive, get a bootable CD/DVD and boot from it.
It will allow you to access your main drive.
If you don't have a built in CD/DVD drive, you need to connect an external one and tell the BIOS to boot from that external drive.

If the main drive is not accessible, it mean that it's dead.
Install a new drive or have someone do it for you. Install a new copy of your operating system. A system restore is ABSOLUTELY NOT possible at this point as the restore data where on the old drive.
ANY data on the old drive are to be regarded as lost. Data recovery lab may be able to recover them, but at exorbitent prices with no guaranty of success.

If you can access the main drive, BACK UP all your data to some external drive. Your old drive should be considered unreliable from now on. It would be a good idea to get a new drive to replace it.

DON'T do a system restore unless you are ready to loose any data and reinstall any programm and application you added and supress any crap you once removed.

If you keep your old drive: Reinstall your operating system. If you have Windows Vista, Windows 7 or 8, you should have an "Update" option. Use it. It will reinstall WIndows while preserving your data and installed programms and applications.
You can get a copy of your operating system from many torrent sources. A torrent site only gives you the information needed to get the requested files, never the files. You need a torrent client. It's a gray area. It's legal IF you do it to reinstall for a valid licence but don't have the regular medium.

Electro
November 2012