Video Converter advice!!

Hi peoples,i have an old xp and i can't run .mp4 (over 950 mb size) videos or 4k videos :)) are too big for my system so i'm wondering who knows a good video converter?i want to convert fast and eficient that videos without losing video quality,i search on google and i met this: MP4 Compressor: How to Reduce and Compress MP4 without Lossing Quality , they said is very fast and convert huge videos to smaller size without loosing the quality, anyone tried this? or some free tool?
thank you

I've been using Handbrake for video conversion for years. You can set the output framesize and bitrate. Later versions are not XP compatible, but you can find XP friendly ones at OldApps -

Old Version of HandBrake for Windows XP Download - OldApps.com

If you are looking to convert huge video into small file size without losing any quality, encoding video to H.265 codec can be a good choice, which helps to deliver the good quality with quite small file size. Some program such as MediaCoder, Staxrip or Pavtube Video Converter Ultimate allows you to encode video to H.265 with fast speed by using the Nvidia NVENC technology.

You might as well give WinX Video Converter a try. It is compatible with XP, supports 4K and many formats, and it can utilize hardware acceleration to make video transcoding much faster while keeping good quality.