I bought a retail version of starcraft 2 when it first came out and installed it on my DELL laptop. I played some of the campaign and multiplayer but just could not handle the low framerate on my laptop so I stopped playing. I recently just got a dedicated gaming desktop and decided to download the game client from Battle.net. Upon finishing the installation and loading the game I discovered that I cannot access the single player. Multiplayer works just fine but the single player is actually greyed out. Does anyone know why this is? Just some extra information: It says that my StarCraft 2 account is Active.

No, idea, Iv'e never tried installing on another computer. Is it uninstalled on your laptop? If not, try that.

Seems to be a known issue based off some googling, have a search and try some of the solutions people have come up with.