Question : Problem: WinXP only recognizes 1 out of 2 GB of RAM, while the BIOS finds both.

After a fresh WinXP install the Hewlett-Packard HP Pavilion dv9000 notebook OS finds only 1GB of ram.
Both BIOS and Belarc Advisor (See attachment) finds both.
I'we tried starting the computer with Ram1 in slot 1, Ram1 in slot 2 and vica versa to see if one of them fails to load the computer - but all posibility's starts the computer..

Also - when I insert the same 2 memory-chips into an equal computer running Windows Vista it finds 2GB..

How to approach this problem?

Answer : Problem: WinXP only recognizes 1 out of 2 GB of RAM, while the BIOS finds both.

Format+Reinstall from another medium solved the problem.