Well if you tried ConvertXtoDVD perhaps a few months to a year ago, the devs have come a long way since then. Do you have a multicore processor running?
I have been following their progress since a fews ago, so give their new version ago.
Also recommended to have atleast 1GB of ram and no other process running.
However do let us know if you do eventually come right.
About WinAVi, if it uses a 1-pass method , then it will convert the video very fast but also cause sync issues with audio and big loss of quality.
As an eg. the videos you see available on the internet (TV Series) , they use a 2-pass encoding system (this is beyond what we are talking about here) however to put it simply, the software you use may have a setting for Good quality, average quality and best quality with speed effecting it respectively.
To better find what you need, you have to go through a trial and error process to find what works.
Ultimately if you don't come right, there are media players going very cheap that will make the process much less painful wrt watching on the TV (i personally think converting to dvd is not worth it) unless it is for a family / friend who just wants to watch something.
For media player suggestions, please look at the following topics discussed not long ago
Media Player Wifi suggestions
Which HD Multimedia player PI
Which HD Multimedia player PII
Good luck
Edit: one last thing to add, if purchasing a sub R700 multimedia player is a no no, then also look at the recent DVD Players (R200-R400) that have the divx logo. YOu simply burn 12 episodes per DVD (350MB per file) and watch it as you normally would. This being a cost effect (cheap) solution

. This was suggested by forumites in the past so just putting it out there. You do have alot of options