Help Me pleaseeeeeeee. I can't understand its concept.

First look at the clock speed of the ram,if both the ram has same clock speed,for eg 233Mhz they will work properly ,otherwise it doesn't work properly.

This should not be a problem because you will simply end up with 512 + 128 = 640 Mb. The only time that it was necessary to use balanced memory was when computers used SIMMs, which would be added as pairs. It is advisable to use memory of the same speed, which is measured as PC400 or PC800 etcetera, because otherwise the 2 will both operate at the bus speed of the slowest.

that is a very obviuos question that crops up with most of the pple...and the answer is as simple as the quetion..there is no harm n usng two rams of diff..apccities as they arent attached anyays...and r independent of functions of each other..so go aheahd and use two diff rams ..no problems at l...

Try to know both memory if they have the same Frequency..look at your memory module they have indicated on its side "PC333 or PC400" something like that.this is rated in Megahertz(MHz).Your 512MB w/ PC333MHz frequency and your 128MB w/ PC333MHz would work together if they have the same frequency. otherwise your computer won't run normally.

It wont cause a problem, go ahead n use the two ram cards, balanced helps as equal memory is used on both cards for shared mem but diff ram size doesnt harm. problem can arise if FSB speeds of the 2 are diff

Some motherboards can access memory in a faster mode if the sims are in pairs ... most computers do not need memory sims in pairs .... they have a 32 bit bus and the sims they take have 32 data lines ... no problems

its ok use those two together. you only need indentical capacities if youre planning to run them in dual channel mode(doubles the ram buswidth). ^_^

It also has to do with the capabilities of your mobo. Some mobos can easily add them up but some mobos will choose the one with the highest ram or they'll choose the one which is the most compatible. Even in terms of fsb speed, you may have 2 512mb of ddr ram but one is just pc333 while the other is pc400 mhz. The system will automatcially step down the pc400 to be compatible with the lowest ram you have which is pc333 but you can still use them as 1 gig of ram.