When you want to get back to your Windows session, it disconnects you immediatly and thus prevents you from entering.
This automatic disconnection is due to the fact that the value "userinit" in the registry has been changed and therefore more advanced on the program of the same name that just handles the user login in Windows.
The solution seems obvious now that you know the cause by cons you can not change this value directly from Windows.
We'll have to go through a Live CD to restore the original value in the following key :
The original value of "userinit" is : "C:\WINDOWS\system32\userinit.exe," (without the quotes but with the comma at the end).
To restore this value, we suggest you use the Live CD "Hiren Boot CD" comprising the program "Mini XP". Once downloaded the Live CD, follow our tutorial : Change the local Windows registry with Hiren Boot CD.