Hi claudegh,
Boot your computer into safe mode and scan your computer with a good program called "Malwarebytes". To boot into safe mode, turn on your computer on and immediately keep on tapping the F8 key. When the safe mode menu comes up, select "Safe Mode w. Networking". After you scan your computer for any viruses/spyware and deleted any infections found, perform a check disk repair on your computer.
Another thing you can do is to scan your computer hard-drive for any errors. You can go to the manufacturer's website of the HDD and download the HDD diagnostics utility program. Put the program onto a CD, boot the computer to the CD, and scan the HDD for any errors. Also, get a compress-air can and point it towards the vents of the laptop and blow out the dust. Hope everything works out for you.