XP Pro SP3 (32Bit) - Upgrade RAM from 2GB to 4GB but shows only 3.00GB

[w3d]

I'm running XP Pro SP3 - 32Bit and have upgraded the RAM from 2GB (4x512MB) to 4GB (4x1GB). I realise the 32Bit OS cannot see the full 4GB, but I was expecting to see nearer 3.5GB (as I have seen reported elsewhere). My System Properties reports just 3.00GB.

When I previously had 2GB installed, the system reported 2.00GB.

The BIOS and the Crucial memory test tool both show 4GB.

I'm thinking I should have saved my money and just bought 2x1GB and kept 2x512MB to make 3GB. But a 4GB upgrade was recommended at the time.

A lot of sites elsewhere suggest that is because of different components in the machine that all take a share of the system RAM. But I don't understand this as when I have less memory in the machine, System Properties shows the full amount of RAM installed.

Do you think this is normal? Where is my RAM?

Thanks.