yup.. XP Professional should do the job.. Just use the upgrade option if you wish to save all your work.. keep in mind that some software and hardware may need to be upgraded.. View Microsoft's HCL to make sure.
You can only install XP PRO over 2K. NOT HOME OR MCE.
What is WPA? Wireless Encryption? If so then you need XP SP2 for that
WPA is Encryption and more secure than WEP but wont run on 2k so wanna put xp on but advised that you can't put xp pro over 2k, a bit confused now, can I put xp pro over 2k? all advice is helpful :-)