Unsatisfactory Service

I have purchased a PC from a computer shop in coimbatore a week back ie.,on 11.07.09.It was an assembled PC,i was told that the installation will be made at my residence and i will have to bear the cost and i have paid for that too.I was promised that the intsalation will happen on 10.07.2009 ,but they did it only on the next day that too after several follow ups over the phone.They did not have the responsibility to inform us till 10.07.09 night 8.30pm .The PC was alredy installed at their shop and had been delivered to our place ,unfortunately there was a power shutdown at my residence and the person who delivered t he PC told that the configuration and the products are installed as per our request and incase of any clarification we were asked to call them.Once the power was on i found that they have installedPentium 4 processor instead of Dual Core 2.5ghz ,also with the printer they have not attached the Black and white cartridge and the sample hseet which has been mentioned in the contents., i have been told that vat charges will be mentioned in the bill and i will have to bear the charges but even that was not mentioned in the bill When i called up and asked they are shouting at me as if they have offered the PC for me without any cost. Regarding the processor part i had to call them for 5 days and then they asked us to bring the same to their shop eventhough it was tehir mistake.when we asked regarding that they said that they will charge Rs.500 extra if they have to come to our place or i have to go in for AMC with them.I dont think that within a week of purchasing a product any one will go for AMC as for the 1st year they will have to do the service.They have also not mentioned the manufacturers details in the bill,I’m not satisfied with the product as well as the service they provide.Kindly let me know is there any way to return the productand get my money back .