The default setting is that this button is enabled. Which means someone
has already defined a policy to disable it. Tell you exactly which
Group policy object is impossible for me to do, as it's specific to
your installation. I can tell you how to find it, and then edit it.
1) Get the group policy management console (GPMC) from microsoft,
you'll need this to edit the Policy.
2) Find which policy is restricting you.
On XP, Open help and support
Select "Use Tools to view your computer information and diagnose
problems"
Select "Advanced System information"
Select "View Group Policy settings applied"
Wait. It will run a minute or two.
Skip down to the section titled "Group Policy Results for <username>"
Scan the "Registry Settings" section for "Remove Lock Computer"
Write down the name of the policy in last column "Source GPO"
3) Edit the policy.
If it is a local policy you can use GPEdit.msc to set the policy on
your machine, or to effect all machines you can create a new policy and
apply it to the ou's that contain your user accounts.
If it is not a local policy you can simply edit the GPO.
As a domain admin, open the GPMC.
Navigate to the "Group Policy Object" Container
Navigate to the policy you wrote down in step 2.
Right click and edit the policy.
In the policy editor, navigate to
User Configuration | Administrative Templates | System | CTRL+ALT+DEL
Options | Remove Lock Computer
make your change.
Exit the policy editor (saves happen as change them, don't worry about
not finding a "save" option.)
close the gpmc
4) Refresh policy
logon/logoff to the workstation. or use GPupdate.exe to refresh the
policy.