guys can i run 4gb(2x2gb ddr 1333mhz) with other higher frequency memory together? :3 thanks in advance guys )
No you cannot.
You can mix and match memory modules, but they must all operate at the same voltage level, timing, and operating frequency.
For example, if you have a DDR3-1333 module, and a DDR3-1600 module, you must run them both at DDR3-1333 for stability reasons. The DDR3-1600 module will most likely run at DDR3-1333 without issue, but the DDR3-1333 is unlikely to run at DDR3-1600 without some extreme tweaking.
In general, mixing and matching modules is a bad idea.