As far as warranty is concerned, if Lenovo have an office in S. Korea they may respond if you explain the situation.
Emphasise that you had to buy a computer in USA because of needing it there - I know from friend's experience with Sony that Korea has a problem with grey market and personal imports, so firms may be deliberately unhelpful if they think you bought abroad to save money.
Failing that, see if you can access the hard drive and put a new one in -- just hope you have an original Windows CD/DVD to reinstall with.