Should i switch from windows xp Professional to ubuntu 10.10?

i have my own laptop which is a kickazz machine... but in my living room i have my old azz desktop which is running windows xp pro and i dont use it but my sister does basically only for social networking(facebook, myspace, webcam) she is not a techie so she doesn't need a ton of software basically just the web browser and doesnt have any files but pictures.... should i completely remove windows xp and install ubuntu( i dont want to have dem both because the desktop has 40 gigs only and i only want one os) give me pros and cons of each and sum feedback please (=