Hi there and welcome to Techimo!!
I don't have so good news for you. The BIOS only supports too AMD 1400Mhz. You need to flash the BIOS to at least version 1005. To be able to flash the BIOS you need to get atleast access to the diskette drive.
I would advise to try running on jumpers and set it to the 1.2 GHz according to the manual. I hope this will get you further in the bootproxcess.
If BIOS version 1005 or higher is installed already, I would advise to clear the CMOS (look in the manual how to do this). I did this to and my PC started without a problem after doing that.
Good luck and let us know how it went
PS sorry for the late reply.