I have just re-installed my Windows, and when i tried to sync my ipad to install new apps, i came across a warning that itunes will erase everything because i haven't copied my old library yet. So i plugged in my HDD and replaced the new library folder with my old one. My apps now appeared just fine in itunes. However, i cannot sync new apps, photos and music anymore, it appears in the itunes that i already copied those stuffs but in my ipad, nothing appears. Any recommendations?