If all you did was erase the videos (versus having a corrupted card issue), you may want to try one of the simple utilities around like PC Inspector File recovery (versus their Smart Recovery Product, which is a more advanced program). It's free and retains the original date/time stamps (which some of the utilities that ignore the file allocation table won't do).
If that doesn't work for you, see this post:
Recovering Images or Video from Corruped Memory Cards
Note that Avira (the anti-virus developer) has a free unerase utility. It's unsupported by them, and I'd only try it as a last resort (since you really don't want to write the card you're recovering files from if you don't have to, so that you don't reduce the chance of recovery). But, if you try the other products mentioned in the dedicated thread above without any luck, you may want to give it a spin at your own risk (simply unerasing the entries it finds that appear to be your video files).