mp4 says disk error

Help. Hubby just bought me of ebay an 8gb usb drive fm rec lcd vidoe mp4 player.  It will not register on mediea player but on computer and all the flies on mp4 say disk error.  Not sure what to do as have no start up disk and really cross as looking forward to using it.  New to this so please not to technical but would really appreciate some help.  Thanks.