Using 2x2 sticks with 2x1 sticks?

[BtK]

My question is this. I currently have 2x1g of Crucial Ballistix 1066. I was going to get Vista 64bit here in a few months and was wondering if I were to get two more 2x2g sticks if they would be compatible with the other 2x1 sticks? Or would I have to get the same 2x1g sticks to match the others?

 

[g-paw]

Should always use matching RAM, in fact best to buy in sets, but if you get another set of the same Ballistix, should be OK. You can get 2 x 2GB for around $85 and either sell the other RAM or just keep, never hurts to have back up parts