Can you press F8 before you see the Windows screen to open the safe mode?
If you can, please find HKEY/......... to find the 'X300 SE128MB BIOS P/N 113-A33406-100 to delete it.
If you can do it, you can turn on the computer easily!
If you can't open the safe mode or you can't find your X300 SE 128MB BIOS P/N 113-A33406-100, please use the 'turn on computer disk' to turn on the computer.
Hope I can help you. :)