Picture of the jumpers please.

Edit: all jumpers off (so none placed at all) on jp12 should give 100mhz fsb. And btw: selecting a 2x multi on most k6-2 cpu's gives you a 6x multi (designed this way so upgrading old non-super 7 boards was possible and people could still reach 400mhz.)

Thank you for the reply but I just solved the problem! I've noticed a lot of dirt around the jumper area and other ''crowded'' areas of the board so I've cleaned it ( warm water and liquid dish soap - after removing the bios battery and all the jumpers ) and after it dried i used contact cleaner on pretty much every contact surface on the board including the jumpers , also I removed the bios chip and used contact cleaner on the chip and the socket , put everything back together , set the jumpers for 100 MHz FSB , multiplier at 4x and it worked. I even run 3dmark99 to check for stability issues.
One other issue is that the external cache is not recognized by windows ( according to Sandra and WCPUID ) and it is enabled in BIOS.

Looking at google images of wcpuid with k6-2 it seems pretty normal. I guess those programs look for l2 cache on the cpu only and don't see the motherboard cache. K6-3 it does display the 256kb l2 cache but ignores (again) the motherboard cache which then really is l3 cache.

Good to hear you found the problem!

I didn't remember if L2 cache was recognized - the last time I had a K6-2 was almost 20 years ago - but I'll run a couple of benchmarks with the cache enabled/disabled in BIOS to see if it makes any difference in Windows.