I just purchased a laptop that has 4GB of RAM in there and it only show up in the System Properties\General as 3.37GB instead of 4GB. When I called HP, the tech support says that Windows XP or Vista will not utilize anything that is over 3.37GB of RAM unless the operating is 64bit. Is this true? I've never heard such thing? Is he giving me the crap on this?

To quote Kurt Angle ~ "it's true, it's true".

Thanks for the response. I guess I never heard that. I always hear users claimed and pc makers claime that their pc can handle more than 4GB of RAM. I wonder why they would say that when anything above 3 becomes useless.

I don't know all the technical mumbo jumbo, but do know that in order to use 4gb or more you need a 64bit OS.

 If anyone cares to know the reason for this is, it is because 32 bit systems have 32 bit memory addresses. 2^32 = 4,294,967,296 each one points to a byte, so thats 4GB worth of memory addresses. Some of this is used for other system things (graphics card and processor and such) so you end up with 3.3GB (approximately, changes depending on your setup) worth of usable addresses. 64 bit systems can obviously point to more memory locations, so we don't run into the same problems, at least until we start measuring memory in exabytes...

Pr1son3r is right. 32 bit operating system just can't address all the memory. For motherboards that state they can support over 4 gb, it's true if they state so. But the operating system is also a factor. I actually have 4gb in a 32 bit os, and my XP only sees 3.2 gb's. It would be 2 gb, but my old modules that I RMA'ed were out of production =P..So OCZ sent me 4x1gb instead ^_^. 

Kamrooz:

It would be 2 gb, but my old modules that I RMA'ed were out of production =P..So OCZ sent me 4x1gb instead ^_^. 

Nice!!!

 Indeed man, it saved me big time considering I tend to have photoshop, after effects, and premiere open at the same time. With my rig, It's hard to have just two open at the same time =P. But the extra memory did make a difference thank god.

pr1son3r:

 If anyone cares to know the reason for this is, it is because 32 bit systems have 32 bit memory addresses. 2^32 = 4,294,967,296 each one points to a byte, so thats 4GB worth of memory addresses. Some of this is used for other system things (graphics card and processor and such) so you end up with 3.3GB (approximately, changes depending on your setup) worth of usable addresses. 64 bit systems can obviously point to more memory locations, so we don't run into the same problems, at least until we start measuring memory in exabytes...

i was also going to say that . BTW is there anything such as exabytes ?

Well, there sort of is, exa is just a prefix multiplier (like kilo, mega, giga or tera) on the word bytes which denotes a size. An exabyte is just 10^18 bytes.

 you will also need a 64 bit processer with a 64 bit os if im right

Yes it is. You'll about 3.25GB of useable RAM on a 32-bit.