Hi, I installed windows xp system on my white mac, it worked normally for one week. But the day before yesterday, I could not access the MAC OS system while I could access windows xp, I backup all the data and inserted disc to repair, and it worked again. But today when I am using it, it suddenly stopped working, I forcefully close it and open it again and the problem happened again! This time I tried to repair, but it showed :Invalid node structure", and I tried erase the disc, but it cloged at "mounting disk", what could I do to make my mac like before and without windows? Thank you so much for your help!!!!!!!!!!!!!