BACKDOOR IS OPEN IN YOUR COMPUTER!!

A guy from california inform me that my computer has a backdoor and that hackers can see me through webcam in my yahoo messenger whenever I'm online and invite a friend to view my cam..

He offered to help me for a couple of times.
But i still doubt him for he wants me to make make an account in LOGMEIN so that he can go to my computer
and change what he have to change.

I told him its risky that way.
when i try to make an account to that site, they inform me that my username or email address has already exist in that site already. I was shocked and become more hesitant to contact him.
I try to change all my passwords in my account and he would said its useless to change my password if my
backdoor is still open.

I erase some files in my environment variables that relates to my useraccounts because i was afraid maybe thats where the backdoor probably located and now i cant open my microsoft word files or any files even photos included to my photo gallery. I know i probably erase an important command in my computer.
I also saw an COMMAND PROMPT in my program so i erase it too.

So anyone can help me with this and what suppose to be done with it.

Thanks for reading my post.

Welcome to Scamwarners.
Webcams can certainly be controlled remotely. See www.boingboing.net/2010/02/17/school-used-student.html
This was done by software installed by the school, so it may well be possible to infect a computer with malware that will do this.
To me, this looks like an attempt to get you to pay to fix an imaginary problem. You only have the word of a total stranger that you have a problem. Trusting someone on the Internet that you have never met, is the basis of all Internet scams.
It would be easy enough for him to create an account in your name on his own website, so that means nothing.
I would run an up to date virus scanner over your PC though. Deleting files usually just puts them in the recycle bin, and they are easily restored. Have you tried this?
If you can't undo what you have done to your computer, I can only suggest taking it to your local computer shop, unless you have a friend who can help. If you don't use your webcam, you could cover it with sticky tape.
What us the site you mentioned?

the one i deleted is like a command.. a variable in my environment..
Its like TEMP and TMP variables..

i delete it since i read in the internet that this two files can be edited to open a back door and a generic code
to access through your computer by adobe files.. or something like that..

this commands cant absolutely be not found in recycle bin..

and oh ya.. thus a COMMAND PROMPT can be seen in my computer normally??
i delete since im afraid he can access to it and change a lot in my program..
This is the disadvantage if we are not a computer geek... hahahaha
All i know about computers are all basics..

I have threatfire and Avast installed on my computer as wel as the normal windows firewall.

A so called layered security works better than just one anti virus program.
These are both programs you can download for free on the internet and i hope it will help you make your computer saver!

I hope i'm allowed to mention these programs?

Guessing you're using some version of Windows?
If you have the Windows CD or a system restore disk, then you can reinstall any critical system files. But any third-party programs will have to be reinstalled separately.

This sort of thing is actually quite common. I'm not sure where these guys get people's phone numbers from, unless they're just going through the phone book.
The two types I've heard of involve trying to take over control of your computer by tricking you into using the Windows remote access feature, or a similar remote access service. Once they have control of your system, the only way to stop them is to pull out your internet connection cable to manually break the connection.
The other involves trying to convince you that you have some kind of computer virus infection and you have to download and run a "fix tool". The catch being that the fixer is actually a trojan that gives them remote access to your system, or a keylogger that lets them see passwords, credit card info, personal details, etc that you're typing in.

Basically if you get one of these calls, just tell them you'll get it fixed elsewhere and get a second opinion from a technically-minded person who you trust.

As for the webcam thing. If you're worried about that sort of thing, just turn the camera to face the wall when you're not using it.

This is EXACTLY why I refuse to use Yahoo messenger,or webcams. I use MSN and thats all,the only people who can see what Im saying are those I choose to talk to. If I get people coming up that I dont recognise,they are immediately blocked.

I have threatfire and Avast installed on my computer as wel as the normal windows firewall.

A so called layered security works better than just one anti virus program.
These are both programs you can download for free on the internet and i hope it will help you make your computer saver!

using more than one anti-virus is bad

they conflict with each other!!

windows defender, windows firewall and ONE anti-virus program is more than sufficient