If your Using x64 Windows loaded stock on the laptop from the manufacturer, its more than likely the manufacturer properly setup the RAM for use in a 64 bit system. If its showing less than 4GB ram in the 'Computer Properties' on a stock system it is also more than likely that a small amount of RAM has been reserved in BIOS to the internal video card.
History:
In many desktops Video Card's have their own RAM, and the rest of the pc has its own RAM- two different physical parts inside. In a lot of smaller devices, weather laptops or tiny pcs where space is low, the video card does not have its own RAM, it shares the overall PC's RAM. So for instance, if you had 4GB and the BIOS was set to dedicate 256 MB to the video card, the video card properties would show 256 MB RAM, and the 'Computer Properties' would show 3840 MB (or something like that) for Windows.
This is normal is cases where the RAM is shared like that.In old laptops, it was set static at like 8 or 16 MB, which is not conducive for gaming. So its a feature meant to give people a small (tiny) boost in the laptops gaming ability. Some BIOS allow you to change the value, to add more or less ram to the Video Card, if say, you do a lot of gaming or not. For example 8, 16, 128, or 256, some even allow 512. Keep in mind though, if you allocate more to the Video Card, your taking ram away from the rest of the system and from Windows, and visa versa.