It's not so much the file size which determines how the video plays, but resolution and bitrate (basically how much information is in each image and how quickly that information changes), which can affect the playback quality.
Things you need to consider are the speed of your computer and quality of your video card, the video resolution and its bitrate to determine how to improve playback.
If there's more information coming in than your computer or Video player can handle, then problems such as deterioration in quality or skipping can occur.
Generally, I can play videos in 720 (HD) & 1080 (full HD) perfectly, with no issues, in VLC Media Player, which is completely free. My computer spec, however, is quite a bit better than yours, which by today's standards is quite low.
In your case, I would suggest you either upgrade your computer entirely, or invest in more RAM and a newer Video Card, as you don't have enough RAM or a good enough card to improve your playback quality by software alone.
Download VLC PlayerHERE
. Give it a go and see if it makes any difference to your playback.
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