The risks of formatting?

Hello! Sorry if I’m redundant, but one can get lost in all these threads. I have a Sansa m250 from which I can’t delete some odd files that have appeared, that the antivirus does not recognize as viruses. I was wondering whether formatting would affect the player software? Thanks.

I reformat at least once a week and have had no problems.

Whenever my m250 starts to get flakey I reformat it.  Solves the problem every time.