does anyone have any thoughts about what could have caused this?

I run xp pro. everything was fine and normal the last time i used my pc., then today things just went from bad to worse. 1st I was unable to connect to the internet. I called verizon, and they were unable to help me. When i logged on, I noticed there were new programs installed I knew nothing about.. (2 of them, one being some on screen keyboard thing , the other was some speech thing.) Anyway, my network adapter seemed to have vanished. So, I did a system restore, from like a week ago. Still no network, but the new programs seemed to be gone. Tried different stuff trying to connect, with no luck. i did eventually find network adapter in "hidden devices" in device manager. I was not able to make it work. Then I shut it down. I noticed that the shut down wasnt how it usually looks... it went to a box with a drop down menu with shut down, hibernaTE, or restart as options. I then went ahead and shut it down. Then, when I started it up again, it looked different also.. and it took me to a windows password box. It had my name already in the top box, and wantd my password. I have NEVER used this windows password thing before.
Also, (two pcs using a linksys box) later on our other pc wouldnt connect... so based on all the stuff i had just been trying on the aforementioned computer, i went directly to device manager, found the network adapter under hidden devices, and found it was suddenly disabled. we enabled it, and it works fine. i am still locked out of the other one.