You might have accidentally deleted key system files, but this is worth a shot:
Recovery Mode for Philips' GoGear
Disconnect the player from the PC, and make sure the mp3 player is turned off. Hold in the volume + button on the mp3 player, and reconnect the player to your pc while holding in the volume + button. Continue holding the volume + for 10-15 seconds until a "Found New Hardware Wizard" pops up. It should recover your device if there isn't anything internally wrong with the player. Warning: this procedure will result in your songs being erased off the player, so they will have to be reloaded.
Philips GoGear Firmware Upgrade
You need to get the latest firmware upgrade from the Philips website:
1. Go to www.philips.com/support
2. Enter your country/language
3. Enter your model # SA6045 or whatever
4. Click on the link for your exact model # (the one w/o the "B" in it)
5. Click on "Software & Drivers"
6. Download the updated "Device/Firmware Manager"
7. Once installed, open the Philips Device Manager
8. Click on the "Update" tab, then the "Update" button (with your mp3 player connected to the computer, of course)
9. Your Mp3 players firmware will update automatically
If you do not have the latest version of the Philips Device Manager installed (the latest is the version from the Philips website), then clicking the "Update" button will give you a false positive saying "The firmware on your device is already up to date."
-Tha Mp3 Doctor