NT can’t restart system

I’m running a Giga-byte m/b with a DEC 1999 BIOS. NT 4 had been running wonderfully on this system. Now when I try to restart the system it completes the write to disk, then freezes as it tries to restart. Win98 *it’s a dual boot) works fine. APM plays no part as I’ve turned it completely off and then on but no change at all. It’s not that hard to hit the reset button but it irks me…appreciate any help.