Philips make several models. But as they are at least a known brand with quite a useful support website you might as well approach them. They may be able to tell you how to place the device in update mode (it's usually a certain key press sequence on the device) and offer you a firmware update that may fix things.
Avoid the temptation to try to format the player on your computer without first okaying this with Philips. You have to be careful not to format in Windows NTFS mode -- players memory is usually FAT32. There have been problems with some Chinese players drastically reducing their available storage space when formatted in Windows.
They may offer to replace the product if there's been no obvious damage by you.