I was hoping to avoid that grief--your right, the cd-key request was a dead giveaway something was wrong.
Look in your C: drive...what do you see regarding WINDOWS
C:\windows?
C:\windows.000
(guessing)
Either way, since the programs are hosed anyway, here is an alternative to wiping all and starting from scratch and losing data...it's just more work.
Using a windows boot disk, rename the following folders c:\windows, c:\My Documents and c:\program files. When you get to the A:\ prompt do it this way
a:\rename c:\windows c:\bakwin
a:\rename c:\progra~1 c:\bakpf
a:\rename c:\mydocu~1 c:\bakdocs
Now, reinstall windows just as we were before. This will create a complete new windows install, but retain your data.
You can recover all your data from the backup folders once you install your programs and you will be able to get on the Internet again. When you get to that point, post back and I will help you along.