I have to increase my PC memory before I can install linux. The problem is that my pc has Rambus "RDRAM" which is outrageously expensive. In my PC now I have 1066 Mhz which is the most expensive. I can get 800 a lot cheaper but I've heard the two chips that I have will run at the 800 also if I combine them with two new 800's. Will this make a big difference and is it worth it. 1066 costs over $100 for used 512mb 1066 compared to about $30 or $40 for 512mb at 800Mhz. I don't have a clue what the difference would be. I only have 256mb now.

I can't speak with a great deal of expertise on RAM, but I'd go for the cheaper option if they'll both work. Something I should note: You actually don't /need/ to increase you memory to install Linux. I've got Debian Linux running on a 400 Mhz laptop with 128 MB of RAM (using the Fluxbox windows manager.) Ubuntu 8.10 is supposed to run on a 64MB machine, although they recommend 384 MB of ram and a 1.2 GHz processor if you want 3D desktop effects. https://help.ubuntu.com/community/Installation/SystemRequirements. They also have Xubuntu which has a more lightweight desktop environment than regular Ubuntu, and would run fine on a 256 MB machine: http://www.xubuntu.org/get. If you are planning to play some powerful 3D games or watch DVDs, the (probably more important) question is: how powerful is your graphics card? You graphics card is what provides the 3D acceleration that speeds your games and videos up.

Thanks, after thinking about it I just wanted the extra RAM to use Linux and stop using windows and my Mandriva disk recommended min. 512mb. As long as I can use Linux I don't care . Thanks again.

From what i know of RAM . If you all ready have 800 mhz ram and if you install 1066 hz it will just run at 800hz any ways because it will default to the lower speed stick. So if you install the 800 hz sticks your 1066 hz will run at 800 hz. It won't make a heck of a lot of difference, if the 800 hz will work with your gear. You won't notice a big speed difference unless you are a gamer. You should be fine with perlcoders suggestion if the ram is compatible with what you already have.

Caveat Emptor! Do read your system documents wrt. memory upgrade/downgrade issues. In some cases you will need to change a jumper on the system board, change the BIOS memory speed settings, or put the slower sticks in a particular slot order, otherwise you may damage the memory and/or the motherboard.