I usually suggest DELL if you don't have a "C Expert" at home -- For normal MS Office and web browsing (if the school need video editing, then you have to pay more than Three thousand something).
Get the 3 year cover for the DELL desktop, call them anytime for query -- the only point I prefer DELL is the service
Remember to ask for student version of MS Office -- as it is much cheaper and licensing software is better.
Call the hotline to see the XP price ... My boss did it at last month for his laptop (yes, for her daughter uses also)
About the Student version of MS Office -- you can ask DELL (don't know they have this offer or not) OR you can ask any software shops at computer malls.