You must download all parts (not just Part 1) into the same folder. Opening Part 1 with a tool like WinRAR or 7-Zip will automatically link the other parts to extract the complete game files.
Do you need help with for this specific game, or You must download all parts (not just Part
Revenge of the Fallen (Windows PC, 2009) Complete Very Good - eBay 2009) Complete Very Good - eBay