Your board supports DDR2 800 so you very likely got a bad stick. I have never heard of Simmtronics but you may want to get a refund. You can also try a different RAM slot.
Yes I said your board supports DDR2 800. That means it's probably a bad stick. It might help if you can get something name brand as well. Corsair, GSkill, Crucial, Kingston, Samsung ect.
one more thing i want to ask is that does bios setting affects working of ram...it was set on 667 mhz i changed it on 800 mhz but it didnt work...i red somewhere that u have to change the voltage too...do i have to change the voltage...and the default is 1.80 volt
What is the listed voltage for the stick that does not work? DDR2 can be from 1.8v to 2.1v. If it was going to work it probably would have worked at 667 though.