i wanna add somethin related to quality and subtitle adds...
if u want best quality avi possible u will have to set ur codec config accordingly...
u can find it as pictured... (just overlook the fact thats all those german rubbish makes no sense to u

)
u will get to this menu
I recommend to just set Bitrate (kbps) to 10000,
u will get a damn hugh avi this way but u can delete it after encoding the avi to Rmvb anyways,
and this way u wont have quali loss from mkv to avi encode...
now to add a sub title file
after u dubble click on the green arrow on taskbar u get to this menu.
here u can browse for ur subtitle files if its not set automatically.
and choose it on the drop down list afterwards.
the "only show forced subtitle" option will keep the subtitle format the sub team originally used...
not activating that will result in the sub title getting Arial and plain white...
since most sub title groups have a pretty nice format for their texts i recommend to use it.