Not sure about this,but if you are not using Media Player,make sure it is not in your start-up sequence or in your startup folder.
The fault is with the exec,which Microsoft needs to address.
By making sure Media Player is not used or started in the background,and following my procedure...( don't forget to APPLY and OK at the end ) , you will nor lose the 1.5Gb of memory.
If anyone else knows a better way,thus allowing you to use Media Player,then please come forward.
This exec is not in the Vista version,if that is any help.