I have a 704 MB MP4 video that I need to reduce. I just did a trial version of Digital Media Converter Pro, which reduced it to 166 MB, but it says trial version of digital media converter pro in huge font on the top of the entire video. Is there any way to reduce the size for free without it putting "trial version" or doing something else to ruin the video?

yo' bonn

you can reduce it free with a tool like Pazera free video converter; does flv, mpegs, avi

you can even do video of same format and adjust the quality to make the size what you want.
You must tinker around with quality settings (i.e. convert as) to get the sizes you want

another tool you can try its very good & will do same is Freemake video converter. Another is VobSo

Third tool is Virtual Dub-Mpeg. This takes some work to learn but its most powerful tool and free,
I recommend if you try this google at Afterdawn.com ->VirtualDub Mpeg it will give links to how to use/learn
It isnt time consuming but you gotta get into VirtualDub. Actually it does things other two doesnt like add 'Subtitles' sync to
any movies needing subs-title.

Either of 1st two very easy to use. 3rd Virtual-Dub mpeg will/can reduce size easily but its more involved. I like VDub
Links listed below ..

Enjoy
http://www.snapfiles.com/get/pazeraflashcon.html

http://www.snapfiles.com/get/fmvideocon.html

http://www.snapfiles.com/get/virtualdub.html