Need Help with SDRAM Upgrade

[Burnselk]

I need help selecting SDRAM memory for my HP Pavilion Model 7955 which uses PC 133 SDRAM. I currently have 512MB (two 256MB sticks which occupy 2 of my 3 DIMM memory slots). I'd like to increase this memory to 1GB (that's the max for my computer) and I need advice. I note that PC133 SDRAM memory comes in different types, like CL 2 or 3, unbuffered (and I suppose buffered?), non-parity (and parity?), ECC (or not), etc. I need advice on exactly what I need to look for and purchase. By the way, HP will charge me to talk to them about this and they'll still be winging it (my own experience). So, I think you guys can help me much better. Do I need to be concerned about putting new memory in any particular slot? Would a third 256MB stick help that much (giving me 768MB)? Would it be worth the effort/money or should I just go for the 1GB? To save money, should I go with two 512MB sticks or would one 1GB stick function better than two 256MB sticks? Is the Cas Latency that important? Is CL=2 better than CL=3, if so why? Any help or comments would be most appreciative. If I forgot about anything important, let me know....I need advice before I go shopping. Thanks guys.