Download key generator for Lenovo ThinkPad T420 Recovery DVD Windows 7 Pro SP1
Compatible with ThinkPad T420s (4170), tested by me personally, it works 100 percent.
Data recovery disks supposedly fit all models of ThinkPad x200s, x200, x201, x220, x301, T400, T500, T410, T420s, T510, T520, W500, W510, W520, Lenovo E120, E420, E520 (after installing the utility you want to run home updates from Lenovo - ThinkVantage System Update, all of the missing drivers will be installed automatically).
HDD will be completely formatted, the existing logical drives removed.
Will be created only drive C and the recovery partition.