Unable to log you on due to an account restriction for all users after virus or spyware removal.

Access to the SYSTEM registry hive. (Access hard drive from other computer, use offline registry editor). Open SYSTEM\ControlSet001\Control\LSA "Authentication Packages" If the key Type is not REG_MULTI_SZ, then delete it. Create new key, as Mutlti-String Value. Name the key "Authentication Packages" with a value of "msv1_0" (without quotes). Several antispyware and antivirus remove that key and recreate it wrong. This is required to log in. I have done this several times to my customers computers, and it always works for me.