electrum doesn't create a wallet.dat file. By default it is electrum.dat. Are you sure you are talking about an eletrum wallet?
Yep. Got confused. I'm definitely using electrum. It's called electrum.dat.
Ok can you tell us what you did and what you want to do now? Number the computers so we understand what you are saying.
edit: for instance what did you do when you imported the wallet? Just copy pasted the electrum.dat file from one system to another ?
Alright. Created on my Macbook Air running Linux. Imported to my Windows PC.
When I imported the wallet, I imported the private key.