Mix 1GB and 2GB sticks of ram in the same machine

Well, it shouldn't matter TOO much, but using two similar strips of RAM would be recommended.

Just found you the Toshiba Qosmio G25-AV513 has a maximum support of 2 GB of ram so I would recommend buying two 1 GB strips or just use one 2 GB.

Your motherboard could have a low maximum of total memory, 2 Gigs in your case. Otherwise your modules could be incompatible with each other. There some possible reasons and usually it is all about motherboard restrictions. For instance it might not support both single-sided and double-sided modules simultaneously. Other typical problems:

The "problem" is simply that different computer motherboards can accept memory in different, but specific, combinations. Some examples:

• Some require that all memory sticks in the computer be identical. So if you have four slots, you can have 4x256meg, or 4x1gig, but you can't mix the 256meg and 1gig sticks.

• Some allow you to mix, but you must mix in pairs. Meaning you might be able to have 2x1gig and 2x256meg.

• Some require that if you mix, you must do so in a certain sequence. So you might be able to put 1gig in slot 1, and 256meg in slot 2, but not the other way around.

• Many require that if you mix (according to whatever other rules there might be), the memory sticks share certain other characteristics, such as speed or others.

So, at least try to rearrange modules in different ways.