Sadly Dell Mainboards are specific too Dell and it's not worth thinking about an alternative replacement, however the suggestion abot consumer rights is a good one as I have found with an Inspiron belonging to a friend that turned up it's toes after just 15 months, if pressured correctly the same person that told you 'No way' will click on an alternate page of instructions on how to deal with 'Someone who Knows the Law' options and you will find they are very helpful, our lass got a brand new one, DHL direct to Paris the next morning along with a very nice 'Were Sorry' grovel note attached.
A quick web search will probaly turn up 'WHICH' and a lot more about this subject so give it a go. Or rather have a go at them, 17 months is pityful really for a Laptop.