iTunes album artwork not showing up

Just got a macbook pro and added my iTunes library from my external HD -- had previously been using iTunes on my Dell laptop. But on the mac, lots of the album artwork that had been on the Dell is no longer there. I selected "get album artwork" but it came back with nothing for virtually everything in the library. An ideas?

Thanks

I am having the same problem, I have about half of my album covers and I want them all. GGRRRRRR

i had the same problem then i figured out why it wasn't getting them all. you have to make sure every song you have that you want the artwork for matches the exact same info as the itunes store (title,artist,genre,album, ect.). if it isnt exactly the same you won't be able to get it.