When is the performance degradation of having 2 memory sticks with different amounts of memory? Computer came with two 512 MB sticks. Decided to upgrade to 2048 so I bought one 1024 Memory Stick. Misremembered(Thank you Roger Clemens for your contribution to the language) that I only a had two slots so I had to replace the original 512 with the new 1024 MB. Computer gave me a nice warning message.

... and the warning message was? Once I thought I was wrong, now I'm not so sure!

Something along the lines of doing this is not as good for performance as having two memory sticks with the same amount of memory.

Ahah yes most likely you will have dual channel capability which means you need to run RAM in pairs. Buy another 1024 stick the same as your other and put it in, then sell the two 512s for almost as much. Epic. Why serve in heaven when you can reign in hell?

Even though it is usually desirable, you really don't need identical memory modules to setup dual channel configuration. BTW, "nice warning messages" is what computing is all about .... LOL!

In my computer I have a 1GB stick and a 512MB Stick. I have had no problems.

I do have dual channel but I am running with no problems at least as fast if not a little more quicker then the old two 512 MB scheme. From what Wikipedia explained that in a dual channel system if you have two uneven memory sticks it will run the higher capacity stick at the speed of the lower capacity stick. So if they are correct I am running at the same speed as the old configuration but more memory is never a bad thing. And I did check my properties and it does show 1537 MB. But still I am probably not getting my monies worth so next chance I get I will buy the second stick. No big rush as I am not a gamer. I just wanted to get early protection against the eventual "Windows Rot" as my computer is now 9 months old. Could have saved money by buying the two together. Live and learn.