OK. I've just managed to solve the issue.
It appears I also had to rescan.
"C:\Program Files\Bitcoin\litecoin-qt.exe" -rescan
So for all those in the near future encountering the same prob as me; these were the steps I had to follow:
- download LiteCore
- synch (which took me 3 days)
- replaced new wallet.dat by old wallet.dat
- run -rescan as per above (which took about 2 hours)
This what's so frustrating about the world of cryptocurrency. It's quite technical, especially when you bought these coins a couple of years ago. If they'd make all this more userfriendly, more people would actually buy