Because Windows XP was a hot pile of garbage.
One day, my network driver broke. None of the discs worked. None of those incoherent "wizards" Windows loves to use worked. Reinstalling Windows broke more things. I couldn't get online for about 2 months.
One day I was at the bookstore and saw a Fedora Core book with an OS disc. I thought it was cool so I convinced mom to get it. Went home, blundered my way through the install and everything just worked.
I cannot for the life of me understand how XP is routinely loved by everyone. It looked like a muddy fisher-price toybox.