1. To Log on to another Administrator account NOTE: If you do not have another Administrator account, then proceed to step 2.
A) Go to the STEP TWO section below.
OR 2. To Boot into Safe Mode for the built-in Administrator account NOTE: You may not need to enable the built-in Administrator account. If this was the only normal administrator account you had, then Safe Mode should automatically boot into the built-in Administrator account.

Tip
A) Boot into
Safe Mode (in Vista) or
Safe Mode (in Windows 7).
B) If Safe Mode did not boot into the built-in Administrator
account, then enable the
built-in Administrator account. If it did , then go to step 2C.
C) Log off in Safe Mode, and then log on to the built-in Administrator account to logon with that account in Safe Mode.
D) Go to the
STEP TWO section below.
1. Backup anything that you do not want to lose in this user account's
C:\Users\(user-name) profile folder,
if the profile folder still exists, to another location, then delete the
(user-name) profile folder.
2. Open the Start menu.
3. In the Start Menu search box, type
regedit and press
Enter.
4. If prompted by UAC, then click on
Continue (Vista) or
Yes (Windows 7).
5. In regedit, go to: (See screenshot below step 7)
Code:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ProfileList
6. In the left pane, click on one of the
S-1-5..... folders (
SID key) with the long number. (See screenshot below step 7)
NOTE: It should have .bak at the end of it.
A) In the right pane, look at the ProfileImagePath to see if this is the same user account that you deleted in step 1 above.
B) Repeat step 6 until you find the one that you deleted in step 1 above.
7. To Backup the Registry SID Key WARNING: You should backup this SID key to be safe in case you delete the wrong one in step 8 below.
A) Right click on the
SID key from step 6, and click on
Export.
B) Type in a name and save the
REG file to a safe location.
NOTE: This is your backup. To Restore the Backup, right click on the REG backup file and click on Merge.
C) Continue on to step 8.
8. Right click on the
SID key, from step 6 with
bak at the end, and click on
Delete. (see screenshot above)
9. Click on
Yes to confirm deletion. (See screenshot below)
10. If there is another
SID key with the exact same long number from step 6 for this user account without
bak at the end, repeat step 7 first, then right click on this same SID key, and click on
Delete. (see screenshot below step 7)
11. Click on
Yes to confirm deletion. (See screenshot below step 9)
12. Close regedit.
13. Log off and log on.