I haven't seen a method that works.
The only way to really remove them, is to black them out and replace with a new sub.
This is a clip using VirtualDub.
The 'Fill' filter used to make a black box and the 'Text to Sub' filter to add new subs.
The new file has to be recoded using the same codec as the source.
IF it's an avi file that was created using the XviD or DivXcodec, then these should be downloaded and installed on the PC.
Google will bring them up.
DivX has a free version for download.
XviD is always free.
In VirtualDub, after loading the AVI, click 'File' > 'File Information' and it will list the codec used.
When saving the new file, click 'Video' > 'Compression' and select the same codec from the list.
An alternative is to try and open the file in AviDemux and saving it as AVI, then opening the AVI in VirtualDub.
The difference is, that in the method shown in the link, the AviSynth script feeds uncompressed files to VirtualDub and there is only one compression step.
The second method has a compression step in AviDemux, then a second compression in VirtualDub.
Apart from the quality hit for each compression, the amount of time required is doubled.
Tks guys but I suppose I'm better off if I try to find another rip without the subs cos I am getting tied up in knots! So confusing the whole issue is...