how much memory do you run?, i am going on a upgrade mission. Options

[Silver]

It really depends on your motherboard.  If you have an older mobo you might not be able to, but if your mobo is DDR you should be fine.  However, remember that your RAM will only go as fast as your slowest RAM chip (i.e. if you have 2700 RAM and 2100 RAM, it will run at 2100 speed, both chips).

If the slot is a different color it is almost always a different type of ram chip; your motherboard would only be able to use one type of ram chip at a time, so if you have 2 types of slots on there the motherboard will only use one type.  If your mobo is compatible, make sure that the new stick(s) match(es) the first one/two you have.  Just be sure to put the largest stick closest to the CPU.

Or in layman's terms, what mobo do you have? 

im looking at this again (ITS TIME!! HAHAHAHAHAHA) and trying like hell to comprehend what she said. i have 133 sdram i can mix 256+512 and be safe? how do you know how many pins i have or can use

[Epacy]

I am running with a Gig of Corsair XMS. Been running that for two years now.

[PISTOFFBAD]

If you are using SDRAM then there may be a compatibility issue. In other words just any RAM may not work. The best way to buy online and get SDRAM that will work is to get it from Crucial.com or Kingston.com where they will match the RAM to your specific computer. I made this mistake with Newegg, the ram was identical to what I had but it kept crashing the pc.