Should I Modify Robots.txt? What is the risk?

[thethinktank]

Hi Sitepoint fam!
I've noticed in my google webmaster account that I've got a significant number of 404s from a recent spider. Having moved hosts and made a few other changes last month, I ended up moving pages to a new folder. Google is still trying to spider those old URLs with the old folder...

I've read that I can make a change to the robots.txt file that will tell G and others to always look at the new URLs for that directory.

Question is: I'm apprehensive to play with the robots.txt file. Is there any risk to my current and future SEO standings to modify this file?

Thanks so much!

TheThinkTank