You really have to lower the quality of the video/audio in order to fit in 8-in-1 or more. Try converting the movies first to lower quality and make sure it's in dvd compatible format so you won't have to convert it again upon burning. Then burn it using Nero or any of your favorite burning s/w.
Anyway, you can use Super, MediaCoder and many more freewares video converter out there. Just look for it. Just remember that video encoding takes up a lot of resources and time depending on the performance of you system.
videohelp.com is a good site for anything about video encoding, converting, etc.