You would want to access the recovery partition. This can be accomplished by pressing the 'F10' or the 'R' key when the system boots. This should load the system recovery tool and you will see a dialog box for conducting a "nondestructive system recovery". If you wish to restore the machine to factory condition (this will not include anything you installed since the original purchase, so you may wish to backup any files you wish to save before conducting this process) you will want to select "next" and wait to be prompted for confirmation and select "yes". When the process is complete the system reboots.
In the case where you seek to conduct a "destructive system recovery" you can select the 'advance' option from the initial dialog prompt in the system recovery and following the prompts as before. If you select this option it will delete the user partition of your hard drive, so unless you have experience formatting HD and installing Windows XP, I would suggest not choosing this option.
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You would want to access the recovery partition. This can be accomplished by pressing the 'F10' or the 'R' key when the system boots. This should load the system recovery tool and you will see a dialog box for conducting a "nondestructive system recovery". If you wish to restore the machine to factory condition (this will not include anything you installed since the original purchase, so you may wish to backup any files you wish to save before conducting this process) you will want to select "next" and wait to be prompted for confirmation and select "yes". When the process is complete the system reboots.
In the case where you seek to conduct a "destructive system recovery" you can select the 'advance' option from the initial dialog prompt in the system recovery and following the prompts as before. If you select this option it will delete the user partition of your hard drive, so unless you have experience formatting HD and installing Windows XP, I would suggest not choosing this option.