Weird thing on my KT4 Ultra

Well my "problem" is that when i increase my FSB (i tried to use 166FSB with 11x multiplier), my computer freezed and clearing CMOS didn't even work...my board said that my memory was either damaged or not installed correctly...ok so i opened my case and removed the memory sticks (2x256MB Spectek PC2100 DDR) and i put firstly one of the memory sticks back...no effect, i removed it and put the other one...success. Then when i put the other one...i got the same error message. Ok now i was worried that i had destroyed my memory module, so i took it off and put it back again (just in case) and it worked again.

Ok now i got to bios and put my settings back to how i had them...restarted and it worked...i went back to bios, put little more FSB (2mhz more), ok everything went fine but then my computer said it didn't detect my Hard-drive and CD-RW, restarted and now it didn't even work...ok so now i shut my computer down and put it back on...worked and i went to BIOS and dropped the 2mhz back to where it was...and now it works again, but i'm really confused with all this...can anyone clarify things for me?

overclocking stresse components and some times if puhed to far they fall over. fortunately for you no perminent dammaga seems to have been done.
what fb are you running at? the memorry will strugle to do 166 all tho with a voltage boost it may.
too try and get 166 DDR333 fsb drop the memmory timings as much as posible nad try again.
you have the 1/5 multiplyer for the pci clock so it wildo 166 (DDR333) as u know.
i sergest that yoo drop the multi and put the fsb at 166 to see if its the cpu or memory thats limiting you.
i expect that its the memmory.
you could use relaxed timing but fast timings/lower latency and a lower fsb often give better memmory bandwidth.

edit : pc 2100= ddr 266= fsb 133
pc 2700= ddr 333= fsb 166