60fps in WoW is just fine, not really sure what you're complaining about here. Its really going to depend on where you're at (city or dungeon? flying, walking, riding mount?) and what is going on around you.
The game is more than just video card intensive. It makes (inefficient) use of all the processor resources that it can get its hands on. What you're seeing is probably not video lag. Could be due to a better MB/CPU/RAM setup on his end. Could be that he's taken better care of his drive, in terms of keeping it tidy. Could be addon related. There's a thousand things that can cause stuttering/FPS issues in the game, most of them NOT graphics related.
So, is he getting 70-80 and you are getting 60? Or is he getting 60 and you're getting 40-50? You've claimed both of these in the same message, so try to clarify it a bit
Make sure your Addons are updated properly, an out of date addon can be causing literaly hundreds of errors per second. this will severly drop your FPS.
Also change your addons depending on what you are doing. When your raiding, turn off QuestHelper, Gatherer and Auctioneer. And when your not Raiding, turn of DBM, Recount and any other raid specific addons.
People are right in saying your CPU is weak, but it should be fine for playing WoW.
I wrote all this and then read that you have just bought it, so you probably dont raid, and your addons are most likely recent.
I would reccomend not playing the game on highest. Some of the details really detract from FPS, and add little in the way of graphical niceness. Turn off Full Screen Glow and Specular Lighting. Shadows have supposidly been fixed, but will still present you with major FPS issues if it gets busy so i keep this on minimum too
With only 2GiB of ram, you may want to turn the View distance down aswell