I just put 1 gig of 400bus ram into the second slot of my K7N2 Delta Series motherboard, I already had a 512mb of 333bus in the first slot. My computer is not recognizing the gig of ram, do I have to change some bios settings, or does 400bus not work with 333bus ram?

you are correct...you cannot mix diff speeds of RAM together. This causes problems because of different settings between the types of RAM.

TKS, I am mixing different speeds of ram right now, I have a stick of 128mb pc133 and another stick of 256mb pc100. I look in my properties and it says 384mb of ram so.....

I have even tried switching the ports and all it shows is 512?

Did you try using just the 1gb ram stick by itself? If it doesnt work it may not be compatible. Here are somes specs on your board http://hardware.gamespot.com/MSI-K7N2-Delta-ILSR-3435-S-35-35 look at the memory in the memory section and make sure you have the right type i.e. pc2100

I tried the 1 gig by itself and my computer just beeped at me and would not load up anything. Yeah, the stick is 400bus aka pc3200 which is supported by the motherboard. I just don't get why it doesn't detect the stick at all.

Probably, but why does it not work?

If it works with the orignal stick and it does not work with the new stick...

It is not compatible...

Sometimes RAM is very fussy about make model refresh etc...

What Brand is the RAM?

I just checked MSI... Your Board, Direct from the MSI site... Highlighted in RED...

NOTE: nForce2 does not support x4 memory for 1GB but it could support other density of dram chip such as x 8, x16...

http://www.msi.com.tw/program/products/mainboard/mbd/pro_mbd_detail.php?UID=436

you are correct...you cannot mix diff speeds of RAM together. This causes problems because of different settings between the types of RAM.

Incorrect. You can mix different speeds of RAM together, but success is not guaranteed. Ensure that the RAM timings set in the BIOS are supported by both sets of sticks and the slower RAM is not being forced to run at a higher speed (i.e. overclocked). Buying the same brand and model of RAM will also increase the chance that it all works.

See here for more information.