I found this suggestion, anyone brave enough to try it ??
http://www.firmware.com/support/bios/cmosclr.htm
Part of the page from there:
When CMOS RAM loses power, a bit is set to indicate this, which should cause the BIOS to detect that the CMOS RAM is invalid and will normally result in the loading of default values.
The same results can be obtained by using a simple DEBUG script to invalidate CMOS RAM. This may be much more convenient than shorting pins on a chip in cases where it is possible to boot to a DOS prompt to run DEBUG.
Here is a DEBUG script to invalidate CMOS RAM. This should work on all AT motherboards. (XT systems do not have CMOS RAM).
A:\>DEBUG
- o 70 2E
- o 71 FF
- q (Quits to DOS)
After clearing CMOS RAM we would usually get some kind of error message on bootup such as CMOS Battery Dead, Clock Chip Lost Power, or maybe just CMOS Checksum Invalid, and default values should be loaded.
The loading of default values after invalidating CMOS RAM is usually more thorough than the loading of default values by choosing the option to load default values in CMOS setup.