I have a Dell Dimension 4100 and I want to change the RAM. I am a bit worried because the website suggests 168 pin DIMM, and most of the RAM that I was looking at is 184 pin. Does this make a big difference? I am so new to all of this and I could really use some advice. I am so frustrated with the proprietary nature of my computer right now! I would prefer not to buy from Dell if it can be at all managed, I was looking at OCZ or Corsair. Any help would be greatly appreciated.

184 pins is for DDR DIMM Memory
168 pins is for SDR DIMM Memory

You want SDR ram for your 4100 Dimension.
http://www.crucial.com/store/listparts.asp?Mfr%2BProductline=Dell%2BDimension&mfr=Dell&cat=RAM&model=Dimension+4100+Series&submit=Go

I am a big fan of crucial and corsair. Never played with the OCZ stuff though.