Check with the company that installed them and ask if the windows are covered by a warranty. If so, ask if the warranties are transferable to the new owners.
When you call, dont tell them the problem. Talk to them as if your interested in new windows and need to know abut the warranties offered with the purchase. AFTER you get the information, call them back and explain your issue to them. It would help if two people made the calls, the first to gather info and the other to explain the issues.