means u have given him 14valid cheques which was cleared and 4 cheques extra cheques which he took from u earlier.
Ur father should have gone with u to buy PC and when it was case of INTEREST/LOAN, he must have gone there, that's the BIGGEST mistake.
U didn't take the bill --- u lost a big proof.
If some ask u why should he consider that ur pc was worth 28800/-, then what will u say since u don't have any proof + u have given 4 extra cheques to him.
Both parties have +/- points... But this happened due to irresponsibility of the OP. Those type of gundas are always in search for Fishes, and he caught u.
The shop owner did a mistake, why didn't he cleared the rest 4 cheques when it was required, why he waited for 10 months to call the buyer.
U gave 14+4 cheques then he should have cleared those in 18 months. Why didnt he clear the cheques?
If ppl started doing like him(that shop owner) then what will happen, shop owners wont clear some last cheques and come after 10 years and show the buyer that total amount is 10 lakhs including interest. I hope everything will be ok for u soon...