sansa media converter n rockbox

what is sansa media converter?n wat’s the use of it?does it have any role in firmware updates?

n also what is rockbox?what all can be done with it?is it safe to use that?do my device funcition properly on using that or is it harmful or cause any virus?do my device function normally if I use that?

n what’s the difference b/w sansa firmware n rockbox?

All your questions have already been discussed in numerous threads here. I suggest you use the Search function to ferret them out.