Is the guest account able to download and install programmes? If yes download and install Malwarebytes free from here
http://download.cnet....72&subj=dl&tag=button
Make sure you opt for the free version. Install it, update it, log out and then restart your laptop into 'Safe Mode' run a scan with Malwarebytes free and remove any nasties found.
Switch off System restore before doing the scan. Once all done re-boot pc as per normal and then re-enable System restore.