Sorry Ken, /3GB has nothing to do with physical memory (RAM), it affects
only how virtual address space is split for given process. (virtual
addressable space per process - 4GB (OS 32-bit)).
I.E. no /3GB - 2GB for user mode / 2 GB for kernel. With /3GB - 3GB user
mode / 1GB for kernel. Doesn't matter how much RAM is installed, even if
system has only 32MB RAM, the numbers are still the same.
Only processes that have largeaddressspace flag on can benefit from using
/3GB.

To OP:
WinXP 32-bit, is 'licensed' up to 4GB of RAM, no matter how much RAM you
motherboard may support, however, because a lots of last gigabyte is
reserved for PCI, in reality, you may see only somewhat around 3GB when you
install 4GB or more. Using /PAE switch in boot.ini may help a bit, but don't
expect miracles, 3.5GB out of total 4 - is very good.


"Ken Blake, MVP" <kblake@this.is.an.invalid.domain> wrote in message
news:%235wkbLU5FHA.1536@TK2MSFTNGP12.phx.gbl...
> IanCoward wrote:
>
>> Are there any limits in the amount of Useable RAM while using Windows
>> XP Home or Professional?
>
>
> It's the same for both versions--4GB. That may be more than your
> motherboard holds, and is probably more than you can make effective use
> of..
>
>
>> Also would using large amounts of RAM cause
>> conflicts elsewhere, with other hardware (graphics cards etc.)?
>
>
>
> No, but to use 4GB of RAM you have to add a switch to a line in the
> [Operating Systems] section of boot.ini. Change /fastdetect to /fastdetect
> /3GB
>
> --
> Ken Blake - Microsoft MVP Windows: Shell/User
> Please reply to the newsgroup
>
>