I have a acer laptop XP 64-bit installed on it .Currently I have 2GB RAM(i.e 2 1024MB sticks).I have only two RAM slots on my motherboard. Now I want to upgrade to 4GB since I want to install Vista-64bit Ultimate edition. Problem is that I checked at the acer website on my laptop manual it says laptop only supports 1024MB on single slot. My laptop can accept PC-4200, PC-5300 667 MHz DDR2 sticks. Just I want to know that if I'll installed 2GB single slot then what will happen or there is the chance of getting some what more memory.Any suggestions will be quite helpful.