I just upgraded my 486 to Pentium MMX with Cyrix 300 chip. After many problems including jumper setting, bad board, lockup on installation I was able to get Windows 95 reinstalled, however it stays on for a few minutes and then does an automatic reboot. This will continue for several cycles never going to the safe mode startup dialogue until it gets a General Protection Fault. Then it freezes. I am using a startup disk that I created with the installation. The hard drive is the same one I used with the 486 board.