crash @ 2000mhz

i just bought so OCZ flex 2000mhz ram. when I took out my patriot ram which was running stable @ 1600mhz, and installed the OCZ my comp crashed. crashed so bad i had a corrupt master file table, which required a format and reinstall. now my comp is running stable with the patriot agian. how do I install the OCZ w/o a crash. the timing can be set @ 8-8-8-30 2000mhz. can i start @ 1800mhz with a way higher # like 10-10-10-35. and if so how do i then back it down. how it the best way to do this. also should I turn on the bios mem tester while im doing this? thanks