Replacement of laptop parts

Hi I had purchased Acer laptop in may 2012 worth Rs 40,000.00 (warranty expired in may 2013). Recently the motherboard of the laptop went dead and I gave it to the service centre for replacement which is worth Rs 17000.00 After keeping the laptop for one week they called me today and told me that the motherboard is not available and they can only provide me a cheaper version of motherboard worth 13000.00 (which is not the original part for my model). My concern here is that motherboard not available is not an excuse as I purchased it 1 and a half year back and its not outdated model. They would have replaced it if I had taken extended one year warranty. As a customer i am ready to pay and I cant throw away 40k laptop just because they dont have parts available. Do I have a solid ground here to charge at them demanding genuine part replacement failing which I can take legal action. I need help from seniors and experienced lawyers. Thanks