Windows XP SP0/SP1

No need to reinvent the wheel, this person has an amazing tutorial that we can use to elevate privileges in this machine.

Windows XP SP0/SP1 Privilege Escalation to System Tutorial

REQUIREMENTS: This article assumes that you have already obtained a low privilege shell on your victim's computer. You have enumerated this machine and concluded that the operating system is Windows XP with SP0 or SP1 installed. If you meet the requirements above, we can continue! This method of privilege escalation relies on vulnerable Microsoft Services. Most services in newer Windows versions (starting from Windows XP SP2) are no longer vulnerable. Vulnerable in this case, means that we can edit the services' parameters.