i just got a new top of the line asus motherboad, okay not top of the line but pretty close, anyhow, i still have win xp pro, and the asus instructions said that 3MB or less was optimal RAM size. DAMN!!! I have 4 slots for dual channel memory and i have pletty of 2gb chips, does any excess RAM cause it to slow down or can i still glean some RAM over 3GB with larger chips?

io is accessed by address bus and data bus, the address bus is to specify where you need to get your data and then the data bus gets your data. as systems are binary, for < 4 GB memory you need (2 ^^ 31) 31 address lines, while with > 4GB its 32 or more
these address can also be used to access your other hardware like video and harddisk size.
although grouping has been preformed in the cpu, speed increases when lower addresses are used.
but when todays professional boards support something like 128 GB of memory, why would you care if 3.5 GB gives better speed than 2x4= 16 GB memory
if you make a nice ramdisk and at boottime load often used files in the memory you will see dramatic increase in speed
mind for power failure though.
and ehm hybernating consumes your memory size of diskspace

commented: Thanks for the help with RAM, i appreciated the details +1

i've been meaning to turn off the hibernating function...how can i do that? as far as the ramdisk and loading oft used files, i'm not familiar with the process, but i'm intrigued, would you mind telling a little more? as far as why i would care about the memory thing it would just be a disappointment....especially considering i already bought the memory like an idiot. my old motherboard, which isn't that old, responded to every additional bit of RAM i put in it, but that could be just because i went from 1GB to 2GB and then to 4GB and at those ranges the amounts are significant

I am at work right now where I am running windows xp with 2 GB memory for which 150 MB is in permanent use.
At home I run Linux opensuse 11.1 with 4 GB and 3.5 GB permanent use.
The performance diffirence is significant with linux as it wins through caching, queues and ramdisks

Most likely your old system has been reinstalled, getting rid of broken installations, unneeded registry keys and a lot of other things that can get skewed.
However with the new windows around the corner, you may need that ram.
open your taskbar and look at the processes that are running. some of them access their associated files quite often.
for example your favorite browser.
before you want to use your browser you could copy it from the harddisk to a ramdisk and run it from there, it means besides the executables, all its libraries are in memory too, when needed they will respond faster.
Microsoft is nasty at making ramdisk available, but you can find it on the installation cd or windows driver kit.
how to use ramdisk
and then what ?
well copy the wanted files to your memory

copy con c:\windows\tord.bat
xcopy "c:\program files\firefox\" "z:\" /v /y

* ^z can be made with shift+F6

and edit your registry to get your firefox files from your ram disk
and look around the registry for the files you have copied
any references to the local harddisk could be replaced by the ramdisk.

Oh and buy an UPS you do not want a power failure !
I chose the browser on purpose as it not so essential.