Watching youtube

If the low-end machine can't handle modern flash player and streaming video, you can always try mobile version of Youtube with Realplayer or compatible software (as instructed on this link).
Or you can can download and convert youtube videos using Tubidy intenret service.

Usually I download videos via tubidy and watch them with VLC palyer...

EDIT: Currently Youtube mobile version uses mp4 and 3gpp video formats, so you don't need any conversion site or program, just download, and use VLC