my y550p came with windows 7 64bit i removed windows 7 and installed windows xp 64bit....i want to know how can i reinstall windows 7?
if you didn't resize your volumes, shut down your computer and press one key recover button to perform clean windows installation.
also, if you install one key recover on xp, try to burn recovery dvds, then use them.
if these solutions don't work, contact lenovo support line and ask for recovery dvds ( lenovo may charge you )
for more information about one key recover, you can check your manual.