You've wiped the system files from the player. If it came with a software CD see whether you can reload eveything from it.

Otherwise, I would prevail upon Argos' goodwill and get a refund -- just say it stopped working and don't mention DRM or formatting.

Bush long ago ceased to exist as a UK manufacturer (it's merely a brand name used by miscellaneous Chinese makers) and I would not recommend you buy another unbranded MP3 player.

Instead look at respected but affordable brand like Sansa and (for a lot more money) Sony.