Most of these devices are not worth fixing nowadays (1 GB or less FLASH memory and/or severe mechanical damages) there were few Philips SA2620 (2 GB) and SA2640 (4 GB) players that were very easy to repair.
After connecting to PC they were recognized either as Mass Storage Device with VID 0471, PID 2030 (most of them) that failed to initialize with error code 10 or as HID device, VID 066F (SigmaTel), PID 3700 (AFAIR only one of the eight pieces).
To fix this problem download Philips Device Manager - software used to restore or upgrade player firmware. Install & run. If mp3 player was not enumerated as HID device connect it to USB port while pressing "backspace" button (at the top of the player), it would be enumerated as HID then and Philips software would detect it and offer fixing it. After 1 minute device firmware would be restored.
Note that all previous FLASH memory content would be erased.