My daughter has forgot what her user password is on her laptop

It depends on where the password is set.  If it's a Windows password, a system restore to factory will clear the problem.  CTRL-F11 at the Dell screen (XP) or F8 before Windows loads (Vista) will get you in.

If it's a power on (BIOS) password, that can only be removed by calling Dell, proving ownership, and being issued the system-specific master password.  If the system is in warranty, the call is free.  If it's out of warranty, a standard $50 support call fee applies.

Yes that will do it.

Dell Factory Image Restore
NOTICE: Using Dell Factory Image Restore
permanently deletes all data on the hard
drive and removes any programs or drivers
installed after you received your computer.
If possible, back up the data before using
these options. Use Dell Factory Image
Restore only if System Restore did not
resolve your operating system problem.
NOTE: Dell Factory Image Restore may
not be available in certain countries or on
certain computers.
Use Dell Factory Image Restore only as the
last method to restore your operating system.
This option restores your hard drive to the
operating state it was in when you purchased
the computer. Any programs or files added
since you received your computer—including
data files—are permanently deleted from
the hard drive. Data files include documents,
spreadsheets, e-mail messages, digital photos,
music files, and so on. If possible, back up all
data before using Dell Factory Image Restore.
Dell Factory Image Restore
Turn on the computer.

  1. When the Dell logo appears, press

  2. several times to access the Vista Advanced
Boot Options Window.
NOTE: If you wait too long and the
operating system logo appears, continue t
wait until you see the Microsoft
® Windows
desktop; then, shut down your computer
and try again.

  3. Select   Repair Your Computer.
The System Recovery Options window appear
Select a keyboard layout and click

  4.   Next. To access the recovery options, log on as a

  5. local user. To access the command prompt,
type administrator in the User name
field, then click OK.

Click

  6.  Dell Factory Image Restore. The Dell
Factory Image Restore welcome screen
appears.
NOTE: Depending upon your configuration,
you may need to select Dell Factory Tools,
then Dell Factory Image Restore.

Click  7.   Next. The Confirm Data Deletion
screen appears.
NOTICE: If you do not want to proceed with
Factory Image Restore, click Cancel.
Click the checkbox to confirm that you want 

8. to continue reformatting the hard drive and
restoring the system software to the factory
condition, then click Next.
The restore process begins and may take
five or more minutes to complete. A message
appears when the operating system and
factory-installed applications have been
restored to factory condition.
Click  9.  Finish to reboot the system.

At system recovery it is still asking for her password , I set up a admin password but it wants hers.:emotion-39:

see this link

http://www.howtogeek.com/howto/windows-vista/change-your-forgotten-windows-password-with-the-linux-system-rescue-cd/

The hard drive data yes.  Any CMOS-based power on or admin passwords will not be deleted, though.

data will be deleted in system disk if i chose to a factory reset. For user password, you can reset the password quite in a few minutes without losing any data on your computer. Create a bootable USB or DVD disk, change the first boot priority, the select the account. Here is the step by step guide: How to reset password of Dell Laptop

The above method seems not working on  Dell laptop ,

First of all , you can reset your dell laptop from password reset disk , but it looks likes you didn't create one , it doesn't matter ,you can set up a password reset disk with USB or CD/DVD , and you don't forget to change first boot device into USB (Reboot dELL laptop and keep pressing "F8" ), in this way  your Dell laptop will be booted from password reset disk (USB) ,

After the Dell laptop is booted from password reset disk , you can remove the old password and login into the Dell laptop without password ,

Next you should know what to reset dell laptop login password 

The hard drive data yes.

You can restore Windows to a backup point when you can remember the password.