To do the format during the installation you need to beable to select custom install. If your OEM disk from lenovo bypass the select normal install, or custom install you have basically two options:
(1) use a 2nd install disk (Can barrow one from a friend) and select custom, then delete partition and recreate the partion - this will fource a fomat.
(2) place the HDD in a 2nd computer, or a USB/esata enclosure and reformate.
If HDD was a Win 7 then you may have a small (about 100 MB partition) - Not sure if best to delete, or leave, as this contains some restore info.