Depending how much HD resolution stuff you have, you can save yourself a lot of time and effort by getting either a DVD player that is UltraDivx certified, or a set top box that plays many formats. I have a WD set top box. Not perfect. Has some flaws, but the picture looks good on my HDTV. The main flaw of the UltraDivx DVD players is they won't play any res. higher than 720x576(although they will upconvert those to HD. Inane but often you have to first down size your video source to then upconvert to HD! Weird!! That's why I ended up getting the WD set top box. To avoid conversion hassles.)
If you don't have HD sources then the UltraDivx player is a good deal at around $50. (Get the HDMI cable at an online discount cable store. Way cheaper than buying at the brick & mortar places.)
You can get free software to do conversions such as DVD Flick
but the conversions take time. UltraDivx players will usually play avi divx and wmv. For mkv you need a bluray player or a set top box or game console.
The big advantage is you either burn a "data DVD" without having to do any conversion or just copy the files onto a HD to hook to your set top box. My WD set top box does not support DTS audio so I have to downmix to AC3. But that's still a lot quicker than converting the video as well.
The WD player has its quirks but the big advantage is it plays .m4v .mkv and even HD res .avi as well as .ts and .m2ts formats. Will play .iso dvd images but does not work well with "episodic" DVDs like TV episodes. Works best with DVD images where there is a "main movie."
The newer WD have automatic DTS downmixing and some other features. I'm still using the generation one WD HD TV player for USB.