which RAM should i buy?..

If you use the Crucial scanner click here it will scan your PC and inform you what RAM is compatible with your system.

It is always recommended to use the same brand. It's also recommended to buy your ram in pairs and configure them in their pairs when putting them onto your motherboard.

While you don't HAVE to match brands, I'd recommended it. Are you aware of the brand/type of your current RAM, not just the speed you have listed above?

Also, the numbers you have provided above don't seem to match speeds of RAM.

yes, my ram is: Mushkin Redline (

yes, my ram is: mushkin redline, and when i checked the RAM itself, its speed said 5-5-5-15 while CPUID says 5-5-5-18. i should get myself one with 5-5-5-15 right?

and also, what i haven't mentioned is that i have DDR2.

5-5-5-15 etc is the Timings and CAS latency, see the charts for DDR2 SDRAM click here

I advise as per The Kestrel says, do a check on Crucial site.

If you mix them pc will only work at the speed of the slowest.

A good explanation on click here

The memory timings are given through a series of numbers; for instance, 4-4-4-8, 5-5-5-15, 7-7-7-21, or 9-9-9-24. These numbers indicate the amount of clock cycles that it takes the memory to perform a certain operation. The smaller the number, the faster the memory.

thx for all the help, i bought ram with same speed and MHz and it works just fine, at first it didnt, but i tryed putting rams in different slots several times and it worked. thx again