Computer linked to Old Computer Help

Computer linked to Old Computer Help
One year ago I bought a New Computer with vista home premium. I had my old computer and my new computer hooked up to my router. My Old computer is xp home.
I reformatted my xp computer, wiped the hard drive, and install some programs like Comodo,Firefox,Roborm, Sandboxie, and Avira. I then gave the computer to a friend. Today he called me and ask me to order some items off the Web. So I went online and went to the web page is was viewing. As I started to order he wanted to follow me so he would know how to do it himself. So he said he wanted 2 of the items I was ordering I changed it to 2. He said cool how did you change it on my page. I said I didn't you must have changed it. I did not touch it. Change it to 3 so I did yes he said mine changed to. Also as I said I reformatted and put all new programs on his computer. He also told be a while back he was trying to figure out how to send Gmail and in the address my son's name came up. When he goes to look at stocks at a web page we both use it sometime lists stocks that he never looked up. Since he just told me this I don't know if they are stocks I looked up or not.
Does this seem like some weird problem with the web site we were both at. Could it be that I had both computer hook to the same router when installing their OS and some how we are Sharing through the Internet. We live in the same town and have ComCast Internet.
I went into Network and Internet setting and changed my computer name. I found that under Workgroup Change Setting
Want do I need to do find out if indeed we are sharing information and how do I stop it. Thanks

 

Weird problem, first make sure your and his remote connection functions are off (if you have not already): Right click on "My Computer" choose the Remote tab and disable this function. Make sure they are not checked.

This should do it.

If not, there are probably identification/addressing problems with the cable service; a call to them should get this crosstalk taken care of.

 

Allow Remote Assistance was not checked. Allow this computer to be controlled
remotely was checked. I think having Remote Assistance unchecked disables allow computer to be controlled remotely. Thanks for the tip. I'll call Comcast, that should be fun (lol)