Having a look through most of the posts being made within the forum quite a lot of problems are due to codecs. Please make sure you have the right codecs (both audio and video) before making a post within the forum.
There are two main codec packs for Vista (both 32-bit and 64-bit versions) which have all the required codecs which are needed for a successful conversion. The URLs below will direct you to the website both the codec packs can be downloaded from.Please remember to remove all existing codecs before installing the packs, if you do not it could lead to compatibility issues.
Vista Codec Pack (32-bit) - Here
Vista Codec Pack (64-bit) - Here
Also be aware that Vista 64-bit uses the 32-bit player as default, you will need to change this for the 64-bit codecs to work. Also installing both packs might solve this problem but might lead to compatibility issues.