Can non-HD be HD?

upscaling a non-hd video to hd/fhd or higher resolution may result in bad picture quality.

Its just like fitting video is full screen

There are some old films I like; but the picture quality is poor.
How to enjoy those films ?
If software can not change anything will we lose the charm of those old films?

^ acquire a blueray/hd version then. no point in upscaling.

Nope.

If the films are Really Old, then nothing can be done, since it maybe that the film were Originally shot with poor quality cams. Although it is highly unlikely, and unless we know what exact movies are you talking about, we can't help much.

Upscaling is a stupid idea.

Get neuview player.
link
Neuview Media Player Professional - Quality Video

The max you could probably do is sharpen the image a little and maybe clean up the colours, but upscaling won't do you any good.