I was using Bitcoin Core qt

My 2 year old laptop couldn't download the blockchain, several days went by
and it was stuck at 2 hours behind...for days....2 hours behind.

So I actually bought a Sager notebook for $1,7000...very expensive, highest scoring benchmark SSD.
It's 20 times faster than my old laptop.  This was mainly so I could get my bitcoins.

I moved my wallet.dat file from the bitcoin directory to an external hard drive.

Then installed bitcoin core qt on my new Sager.
It downloaded the entire blockchain in 15 minutes as I recall--extremely fast.

But now when I double-click the wallet.dat file (and bitcoin qt core program opens it),
I get this message:  "Bitcoin Payment Request File Handling- payment request file cannot be read.  This can be caused by an invalid payment request file."

Does anyone know what I did wrong??  And how do I open these wallet.dat files?

Thank you!