The software you used to convert must have changed the framerate, see if it has a setting that allows you to either select the correct frame rate for your tv system (PAL - 25fps or NTSC - 30fps) or allows you to enter the correct number. What spec is your computer, how much memory does it have, what type/speed of processor(s) does it have, how much free space is on the hard disk, is it a laptop or desktop model?

Answer these questions first before you go out spending money on a new computer that you may not need. Video files on DVD disc are more prone to problems that other kinds of video files, a lot of the popular editors and supposed 'convertors' don't work well with them, try downloading a 30 day trial of the latest version of Sony Vegas to see if that helps.

__________________
Better than a poke in the eye with a pointy stick any day...