abdietea, I have uploaded a copy of s1fwx with all the batch files you will need
HERE
Extract the folder and put your dump.bin into it ( it must be named dump.bin) and run the repair.bat. If you did not repair your dump when you extracted it it should be ok now and you can try to load it to your player. If you get an error message when you run the repair.bat the dump has either been repaired already or contains errors and you will not be able to use it.
To do a merge you need to place your repaired dump into the folder (named dump.bin) and a full version firmware (named full.bin). Running the merge.bat will extract all the files from your dump and load then into the full version firmware overwriting any files that already exist with the same name. You will then get a file called merged.bin which is the merged full version of your dump.
This does not always work and you may have to try merging your dump with a few different full version. Hopefully you will end up with a working full version of your players firmware.
Make sure when you repair or merge firmware that you only use copies of the original files. If you use the original and destroy it you have lost it.
Hope this helps.