I have a second PC that currently has two sticks of RAM, 4gb-2600hz (8gb total). Then I have 4 sticks of 2gb-2600hz RAM left over from my other PC, is it possible to put two of the 2gb sticks with the 4gb?
Check the latencies on the memory, if they are similar then there will be no problems. The latencies would be something like "8.8.8.26". If you do not know this, share the model number of the ram with us and we can check for you.