Lenovo 3000 C305 All-In-One - Manual (Page 6)

4 Windows7 Upgrade Instructions
5) Users have the option of selecting
“Upgrade” to upgrade the current system
directly or “Custom” to install a new copy
of Windows7 to a different disk partition.
6) Choose the target installation partition
in the custom window.
Attention: To upgrade the system you
must format the target partition, which
will cause loss of data and files. Be sure
to backup data and files before
upgrading.