Windows 7: Question about RAM on Windows 7 Ultimate x64

As far as I know, depending on what bit a computer's OS of Windows 7, the RAM that the computer can use will vary. So, if I'm using Windows 7 Ultimate x64 as my OS, how big of a RAM can it use for the system?

Likely it will be the maximum supported by your motherboard.

Windows 7 x64 Professional and Ultimate maximum supported RAM, 192 GB.
Windows 7 x64 Home Premium maximum supported RAM, 16 GB.

So the amount of RAM a computer uses would be dependent on what the motherboard supports and not on the OS itself?

I'm not sure what you're talking about. It seems you're referring with mainframe or some super computers with this spec, but I'm asking for the laptop / desktop ones. This laptop has 4 Gb RAM in it and has Windows 7 Ultimate x64 as its OS, but only uses 3.73 Gb of that 4 Gb total RAM. How come then this is the case if a x64 Windows 7 Ultimate Edition can use as far as 192 Gb of RAM?

Its perfectly normal for your laptop to use only 3.73GB since you have an integrated graphics card which 'shares' its memory with the RAM

Windows 7 Ultimate x64 supports up to 192GB but the maximum amount of RAM is limited to the laptop's board, most current laptops support up to 8GB

I had this statement: "Sorry for being rude, but apparently you're not giving me the right answer for my question. ." omitted since I found out that the person who posted it was right. You're right as well with the fact this laptop uses a shared memory from RAM as its video memory which I kinda didn't notice earlier lol. Thanks for the info.

It is a double edged sword, really. The amount of RAM that can be addressed is limited by 32 bit software, but your motherboard does determine how much memory is available to the OS in the first place.

I see. Thanks.