said by oldITtechie : YOU ARE CORRECT!!!! (and they are wrong) Their is a file stored on your computer when hooking up first time to xfinity, at least as recently as 1 year ago. I had protection on my browser that stopped them from downloading, so the install kept failing. After a time they would HIJACK my browerser and make me "setup" again, but it always failed. The people on the phone at support didn't have a clue.
I finally figured out by turning off my protection, letting them install the little file they check for, then turning the protection back on.
This was not the toolbar, but something to make life easier for Comcast. I don't remember the details, but I found the answer and filename by searching the internet, not on Comcast support sites!
Good luck!
If what you say were true, every time a customer connected a new PC, or allowed a guest to connect, they would be redirected to the walled garden modem activation site.
The only "file" is the database record on a Comcast server that identifies your modem's MAC address as being associated with your account. There may be cookies installed on your connected PC(s) when you visit any Comcast/Xfinity web site (including the walled garden modem activation site), but that is only if your browser settings allow it to happen, and those cookies are in no way required for you to use the Comcast service. You also may be encouraged to install the Comcast toolbar (and/or other Comcast branded software) on your PC(s), but again that will only happen if you allow it to happen, and not installing such software will in no way keep you from using your Comcast connection.
Within the past several weeks, I have activated two new modems, and I was not even offered any Comcast branded software by the walled garden site, because I was using a Mozilla based web browser that does not support ActiveX controls being installed. But even if you use a browser that does allow ActiveX, you do not have to permit any software (including some mythical/mysterious file) to be installed in order to simply activate a specific modem for use with your account.
The OP at some point apparently allowed the Comcast portal page to be setup as a Google Chrome homepage tab, but that has absolutely nothing to do with being redirected to the walled garden modem activation site (if that is indeed what is happening to the OP).
There is a very good reason why you don't remember the details.