Did not need password before now need

[mrel]

Hello
Have Dell optiplex Gx240 desk top computer.
All sudden got this problem with the computer.
The problem is I use to start up the computer with out using a password.
One day i was trying to setup dialup network,so I start press some boxs ,I don't remember which boxs i press.
So close down the computer for the few minute.
Now when i restart the computer my screen say i need a password , before I never use a password to get to the desktop.
So now i need to type the word administrator to get the deaktop.
When in administrator i notice All my folders on the desktop are gone.
Who know what is wrong with the computer ,how do i fix this computer.
Thank for the help .
mrel

 

[kimsland]

Start > Run > control userpasswords2 > ok
Tick the box "Users must enter a username and password to use this computer"
Click to highlight your Username
Click Apply
Untick the box: "Users must enter a username and password to use this computer"
Click Apply
Click OK
Click OK
Restart

 

[mrel]

Kimsland
Start > Run > control userpasswords2 > ok (Did this)
Tick the box "Users must enter a username and password to use this computer"(did this)
Click to highlight your Username (this part Did Not show up ,this part with my username did not show up on screen)
Click Apply
Untick the box: "Users must enter a username and password to use this computer"
Click Apply
Click OK
Click OK
Restart
mrel

 

[kimsland]

Click to highlight your Username (this part Did Not show up ,this part with my username did not show up on screen)

Therefore your original UserName does not exist any longer

Actually, reboot to "Safe Mode" by pressing F8 before Windows starts up
Log on to the Administrator account. Then do the above again

If all else fails, Just do this: Start > Run > C:\Documents and Settings > OK
Do you see your original UserName?