Playing the Sims 3 without a disc

Hello! 

About a year ago, I purchased the Sims 3 with a disc, and I downloaded it onto my PC with no issues. I recently went to download it onto my laptop, and so I logged into my Origin account to find that it was already located there, no disc needed. I was able to download it and play it without inserting the disc. When I attempted to play it on my PC, however, I found that I cannot play it without the disc... which is a problem as I do not know where it is. 

Is there a way that I can 

a.) uninstall it and keep my custom content 

b.) reinstall it so that I do not need the disc to play, I can just download it from my origin account. 

(I'm sorry if this post is jumbled, thank you very much for your help!)