I restarted my desktop after an hour or so's absence during which I had left the modem on. I raised Google Chrome and tried to log into PayPal. A black and white msg came up warning me not to switch off because my computer was compromised and ordering me to call the above number. I heard a screaming beep beep warning until I switched off my speakers. I rang the number and a male asian voice asked who is my virus protector. I told him I couldn't remember and it was a free one anyway. He told me I must buy one and that he needed to check something on my computer. He asked me to go to 'windows symbol r' and type 'h tt'. I thought then that he may be trying to get control of my system for nefarious reasons so I said "hang on a bit" and waited. Naturally, he hung up.