My Mp3 keeps randomly deleting songs.. anyone know why?

i had a full Mp3 yesterday. now, when i plugged it into my computer, i noticed all the songs are almost gone. i have 24 songs left. it's, 796 MB remaining. when i had a full space before. i don't know where the deleted songs have gone... it's done this before, and i don't know why... i have a Philips Mp3 btw. that has 1 GB. can anyone help?