InterVideo WinDVD 6 - issues with file capping

When i'm on WinDVD 6, i can cap DVDs all perfectly fine...but when i try capping from .avi's .mpg's etc. the two different camera boxes are completely greyed out

What could i be doing wrong?

I've looked through the memories, and i only found people who couldn't cap from their DVDs, which didn't help...

Any help is greatly appreciated, thankyou in advance!