Supposed to be 512mb but only allowing...

Question

I bought a player off the dreaded EBAY, sold as a 512mb player. I have plugged it in to transer files but only allowed 14 songs on or so. I checked the capacity and indeed it is 512mb (478mb to be exact but close enough) but when everything visable is deleted it leaves only 148mb of memory available. Surely the software running the player can't be 300mb or so!!!! Even if it is, surely its a bit unfair to sell it as a 512mb player if you can only use a 1/4 of it!!!! Any idea's anyone? Guy I bought it off isn't being very helpful at all!!!!!