My T400 machine seems to be showing about 100MB less in available RAM that I would expect. I presume this is so due to the ATI graphics on my machine. However I am still unable to recover the 'lost' RAM even after disabling the program. Is there any way for me to get the lost memory back?
The RAM is not really missing - see this related Microsoft KB article. The RAM may be used by other devices in your computer and their reserved memory, as well as the configuration of your BIOS and settings, your version of Windows - XP, Vista Windows 7, and other system settings.
The amount of available memory displayed may also change depending on wether the BIOS is set to integrated, discrete, or switchable video mode.