It isn't clear from your post whether you are having problems now, after the phone tech guy finished whatever he was doing.
It would not be normal for Windows to return to the welcome screen, or password screen, but if, after a reboot, you can now access Windows through your account, and also access the internet through your new DSL network connection, then I would accept this as a "Windows thing". It happens occasionally,
Let us know if you are having problems though.
OK, this may be a bit vague, but here's the situation. I run windows xp, have no issues whatsoever, I have administrator rights and have a password that I need to enter on the account page. I had a telephone company tech come last Monday to hook me up to DSL instead of the dialup, **sorry I wasn't there to see this, but was on the phone with my husband and the phone tech**...they put my password in, it said it was loading my personal settings, briefly showed the desktop and went right back to the page where the password needs to be entered. Apparently it did this over and over again. The PC was functioning perfectly four hours before this. All I did was disconnect from my dialup, close all my programs and turn off the monitor. So could it have been something they did while installing the dsl, a change in the settings ??? It just doesn't seem that should have changed anything. There was no software to load or anything, just a line to the router, router to pc. Just loooking for some general info. Thanks in advance.