1gb gtx 560 + 4gb ddr3 ram at Win7 32bit - Does Gpu ram is 1gb???

It's not true. Your system RAM is used by your processor, while your VRAM is used by your graphics processor, so they have two separate arrays for memory addresses. The limit comes from simple fact that address length is 32 bits long, therefore it can only store 2^32 different addresses, and that is exactly 4 Gigabytes of data. However, since VRAM have separate addresses, it gets separate limit as well.

so my graphic card isnt getting limited right now? it has full power?

Yes

Wait, you telling us that there's no necessity that the OS map all the memory in a single memory address array? For example: CPU cache, HD cache, DVD-R cache, bios onboard memory, ram memory, video card ram memory. Where would they be mapped?

How can the OS or CPU 'see' or point the video card ram memory or the cpu cache?

SO need to point, or make a 'chart' of the address of each memory of the PC, and 32bits are limited to 4GB. (You could think that the SO uses pointers, or vectors to show us the address of each part of memory)

32bits OS have the 3gb to 4gb named as Upper Memory Area.
This area is RESERVED. So you only uses 3gb for softwares/OS or any application that runs in your PC. (You're "losing" from the start a full 1gb)

In the reserved area (the other 1gb you have) is where enters all the other memories, including, HD cache, chipset, mobo internal memory, VGA memory, all of them. Considering that ALL the memory you have (besides the cpu memory ram, and VGA memory) is, for example, 100 megabytes. This leaves you with 0,9GB for a videocard. Saying this I can assume that you won't using all your main memory, neither using all your VGA memory

Actually, CPU isn't using VRAM. Only the graphics processor has direct access to it.