Just to add some information here, the reason why you can't log in if the Windows User Account password is blank is due to a Group Policy setting that limits the use of blank passwords to local console logons only.
In this case, It is best to assign a password to the Windows User Account. However, if you are unable to assign a password, you can disable the policy by following the steps below (caution: use the GPO editor at your own risk):
Use the Group Policy Editor in Windows XP:
- Click Start, and then click Run.
- In the Open box, type mmc, and then click OK.
- On the File menu, click Add/Remove Snap-in.
- Click Add.
- Under Available Stand-alone Snap-ins, click Group Policy, and then click Add.
- If you do not want to edit the Local Computer policy, click Browse to locate the group policy object that you want. Supply your user name and password if prompted, and then when you return to the Select Group Policy Object dialog box, click Finish.
NOTE: You can use the Browse button to locate group policy objects linked to sites, domains, organizational units (OU), or computers. Use the default Group Policy Object (GPO) (Local Computer) to edit the settings on the local computer.
- Click Close, and then in the Add/Remove Snap-in dialog box, click OK.
The selected GPO is displayed in the Console Root.
Under Local Computer Policy > Windows Settings > Security Settings > Local Policies > Security Options, disable the policy named Accounts: Limit local account use of blank passwords to console logon only.