There was a similar problem on my computer you know, I tried using a CAT5 to transfer files but it wouldn't work. Ultimately, I setup a connection and in linux and it worked....
But one word of advice, forget the CAT5 as far as large files are concerned because it is REALLY slow, and by really slow I mean like 56k speeds... lol. A Lan Card is the way to go when you want to do this or just get your fiance's hard drive and put it into your PC and transfer the stuff, Cat5 is the worst way to do it...