John from Oklahoma writes:
Had a person call who stated he was a Microsoft maintenance representative and it had been reported that my computer was showing a lot of error and warning activity which was causing it to run slow. I have a PH Pavilion computer with Windows 7 bought in April 2011. To prove this he had me type in “eventvr” in the search programs and file start box. This brought up event viewer and under administrative events a list of errors and warnings. He had me try and delete them(today over 9800). Of course, I couldn’t. He stated these errors and warnings were a problem and were causing my computer to run slow. He wanted to connect me with his technician who would walk me through getting rid of this problem. Being leery, I thanked him and told him I would call him back after I researched this problem, if I needed his help. He was not a happy camper. In reviewing the errors and warnings shown, messages, such as, Dhcp-client, print services, kernel-eventtracing, application virtualization, etc…, I noticed that a lot of this activity was taking place late a night or early morning when my computer was supposedly turned off. Last night for instance, over a hundred errors with the source stated as cdrom. I do run ccleaner and Norton each night, as the last thing I do, and have Norton turn off the computer after it is finished. My question, should I be concerned? If so, what can I do to fix the problem and how do I keep it from happening in the future?
John, you should be leery. Microsoft does not call people at home about their individual computer issues, period. If someone calls you up out of the blue and says they are working for Microsoft and have called to fix an error, they are flat out lying.
Errors reported by Windows are compiled and used to create future bug fixes. They are no responded to on an individual basis. You are certainly not alone in being targeted by this scam and it has been going on for years.
Anyone who pulls up event viewer is going to see a lot of activity. Below is an example of mine and my computer is running just fine. Most of these events are minor and just par for the course of PC operation.
These scams end with the crooks asking you to pay several hundred dollars to fix the “errors” on your computers. The event viewer is not slowing down your computer. Unless you’ve noticed an issue with your computer, it is probably just fine. And if there is an issue slowing it down, the guy on the phone doesn’t have any solution but to empty your wallet. Running Norton and CC cleaner are great measures to take care of your computer. So is hanging up on crooks like the guy who called.
Microsoft suggests you contact local law enforcement and also the FBI’s Internet Crime Center at this link. 
It doesn’t sound like you gave these guys access to your computer, but if you did, change all of your account passwords ASAP.