Webcam was interferring
Thanks Raybay but I think I have found out what is causing all the problems. I have installed a Logitech E2500 webcam and the instruction manual is very sketchy, only giving you instructions on how to install the programme. When you right click the webcam icon and then go into Properties, Compatibility, it has ticked "Run at 640 X 840 screen resolution" whereas my screen is set at 1024 X 768. Each time we started the computer (we put it to bed at night), the computer adhered to the webcam screen resolution and not the Windows setting and my pages were huge. I had no idea what was going on until I found the answer about screen resolution on this site.
Also, when I installed the programme, I did not disable my firewall and shield and a technician at Logitech said that the programme would not be installed properly. So I have uninstalled, disabled firewall etc., and reinstalled the programme. Now it doesn't seem to freeze the screen nor crash as it did before. I sent a webcam to my parents in Cyprus and my sister in Devon and am waiting for them to fix theirs so that I can test it out.
Thanks for your suggestions and help.
compused!