Upgrading RAM problem

[Tim Hall]

This laptop has two memory slots, initially with 512MB in each.

I ran the crucial.com scanner and it said I could upgrade to 4GB in the shape of two 2GB sticks, which I did.

Fitted them both and machine says it's only got 2GB.  Refitted them and got it up to 3GB.

Fitted one only. 2GB.

Fitted the other one only. 2GB

Fitted one only in the other slot. 2BG.

Fitted both, had a look at the BIOS setup. 4GB.

Saved settings, booted into windows. 3GB.

Help.

[Biggsy]

What operating system?

32-bit Windows can't use 4GB.  Can only use 3.something.

[rusky]

What version of windows? XP will only use &  display approx 3GB

[Polar Bear]

32 bit installations of Windows cannot access much above 3gb of RAM IIRC.   

[Polar Bear]

Oops.  Many cross posts 

[Tim Hall]

All with the right answer. XP, innit. Thanks for quick responses.

[Biggsy]

I got 4 GB for my PC running 32-bit W7 even though I knew I wouldn't be using all of it.  It was cheaper than 3 GB at the time and place.

[pcolbeck]

32 bit OS can only address 4Gb of memory as 2^32=4,294,967,296 ie 4Gb.

The reason you cant actually see 4Gb of RAM though is specific to x86 systems (with any OS not just windows) in that you use some of the address area to access things other than system DRAM. The memory on graphics cards for example plus hard drives and other devices. All this eats into the address space meaning that you cant access all of your 4Gb.