As you appear to be runing out of memory, I assume that you have closed down any other running programs when trying the merge

I would suggest that you spilt your donor file into [say] 4 sections see

http://ftm.custhelp.com/app/answers/detail/a_id/3669/kw/spli...

Now compact your main file and the 4 donor files (call them D1 through to D4)

Now merge D1 with your main file

Set the merge threshold to around 500

Save and compact the file

Now merge D2 with the main file + D1

Repeat the backups and compact

Repeat until you have all the parts merged

Now run the usual find duplicates etc, and generally clean the file up

Depending on the source of the donor file you will also probably have to clean up, the places and sources etc

John D