It's not so much the way it is meant to be, but rather that there is not alternative other than using 64-bit. Allow me to explain.
Humans think in decimal (0..9). To calculat the total numbers that can be represented by any given number of digits, you use the formula 10^X, where X is the number of digits in the number. Thus 10^3=1000 because a 3 digit number can represent 0..999.
Computers "think" in binary (0..1), and the same rule applies to calculate the maximum number that can be represented by a binary number. 2^X, where X is the number of digits in a binary number. Thus 2^8=256, because an 8-bit binary number can represent 0..255 (decimal).
Following the same rule of 2^32, you get 4,294,967,296. This is the maximum address space therefore that can be represented by a 32-bit address.
4,294,967,296 Bytes / 1024 = 4,194,304 KB
4,194,304 KB / 1024 = 4,096 MB
4,096 MB / 1024 = 4GB
The reason why your system shows 4GB installed, but only 2.99GB as usable, is because the deficit is already in use - by hardware, and the address spaces given to every device must be allocated somewhere within the 4GB limit. Devices such as timers, keyboard controllers, usb controllers, irq controllers, bios, etc must each have at least some memory allocated in order to function. Anything and everything that is part of the motherboard internal functions, or an expansion slot. This allocation happens on the hardware level, and whatever remains is available to the system, and varies depending on configuration. My old motherboard, when using a 32-bit Windows, showed 3.5GB available.
The only open alternative to you would be to either get a better motherboard that makes more efficient use of memory, or to change to a 64-bit operating system. Switching to 64-bit is the better choice, not the least of which would be because of enhanced security and stability.
