Lost Main Account After Upgrade

Question

I just installed a security update. After the restart, I am taken to the log in screen, but my main account is not one of the options. It only shows my sister's, which was created just for a weekend (in other words we don't remember the password). Occasionally it goes from my sister's as being the only option to "Other". When I click to log in as other it asks for a name and password. I have used my accounts name and password, but it won't accept.
Does anyone know what has happened and how I can fix it?
Thanks.

Answer 1

Hi scarecrow02b, and a warm welcome to the forums!
First we should do this to help make sure the rest works right...
"Try Disk Utility
1. Insert the Mac OS X Install disc that came with your computer, then restart the computer while holding the C key.
2. When your computer finishes starting up from the disc, choose Disk Utility from the Installer menu. (In Mac OS X 10.4 or later, *you must select your language first.)*
*Important: Do not click Continue in the first screen of the Installer. If you do, you must restart from the disc again to access Disk Utility.*
3. Click the First Aid tab.
4. Click the disclosure triangle to the left of the hard drive icon to display the names of your hard disk volumes and partitions.
5. Select your Mac OS X volume.
6. Click Repair. Disk Utility checks and repairs the disk."
Then Safe Boot off the HD & use Disk Utility from there to Repair Permissions, reboot once more. (This step rarely works for this problem, but has a couple of times).
applesetupdone...
http://discussions.apple.com/thread.jspa?messageID=6059333&#6059333
http://www.askdavetaylor.com/howdo_i_reset_my_mac_os_x_admin_rootpassword.html
This was Posted by: JoseAranda at September 9, 2006 3:48 AM
"OK, restart your computer, hold down Command-s and type in the following:
/sbin/fsck -fy Enter
/sbin/mount -uaw Enter
rm /var/db/.applesetupdone Enter
1. The rm command is the remove command which deletes the file.
2. Robert: I'd rename the file via: mv /var/db/.applesetupdone /var/db/.applesetupdone.old
reboot Enter
Once you've done that the computer reboots and it's like the first time you used the machine. Your old accounts are all safe. From there you just change all other account passwords in the account preferences!!
end of posted by: JoseAranda"
Once you have a new administrative account, you can change of your old administrative account
blue apple > System Preferences > Accounts