A firend shared a video with me and they say it plays fine for them on Dropbox and on their PC.... when i try and play it says 'Unable to preview this item.'.... when i download it, it won't play in any media player at all...
There are 20 GB bandwidth limitations set per day. This means that every file, photo or video that's viewed and/or downloaded counts against your daily allotment.
EXAMPLE: You share a link to a 500 MB video (0.5 GB) and it's viewed 40 times in less than 24 hours, then your 20 GB bandwidth limit for a free Dropbox account has been attained (your links will be temporarily disabled, and anyone who tries to access them will see an error page instead of your files).
Keep in mind that if you share a link with people who in turn shares the link with their friends, especially via social media, then your bandwidth limit could be reached in an hour (not hours).