32 and 64 bit versions for Windows 7

The main differences between the 32-bit versions of Windows 7 and the 64-bit versions of Windows 7

Architecture	Windows 7, 32-bit versions	Windows 7, 64-bit versions
System requirements	1-gigahertz (GHz) 32-bit (x86) processor or 64-bit (x64) processor, 512 MB of RAM	1-GHz 64-bit (x64) processor, 1 GB of RAM (4 GB recommended)
Memory access	A 32-bit version of Windows 7 can access up to 4 GB of RAM.	A 64-bit version of Windows 7 can access from 1 GB of RAM to more than 128 GB of RAM.
Memory access per edition	All 32-bit versions of Windows 7 can access up to 4 GB of RAM.	Windows 7 Home Basic - 8 GB of RAM Windows 7 Home Premium  - 16 GB of RAM Windows 7 Ultimate - 128 GB of RAM or more
DEP	32-bit versions of Windows 7 use a software-based version of DEP.	64-bit versions of Windows 7 support hardware-backed DEP.
Kernel Patch Protection (PatchGuard)	This feature is not available in 32-bit versions of Windows 7	This feature is available in 64-bit versions of Windows 7. Kernel Patch Protection helps prevent a malicious program from updating the Windows 7 kernel. This feature works by helping to prevent a kernel-mode driver from extending or replacing other kernel services. Also, this feature helps prevent third-party programs from updating (patching) any part of the kernel.
Driver signing	Unsigned drivers may be used with 32-bit versions of Windows 7.	64-bit versions of Windows 7 require that all device drivers be digitally signed by the developer.
32-bit driver support	32-bit versions of Windows 7 support 32-bit drivers that are designed for Windows Vista.	64-bit versions of Windows 7 do not support 32-bit device drivers.
16-bit program support	32-bit versions of Windows 7 support 16-bit programs, in part.	64-bit versions of Windows 7 do not support 16-bit programs.

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DIFFERENCE BETWEEN 32 AND 64 BIT WINDOWS

The main differences between the 32-bit versions of Windows  and the 64-bit versions of Windows  relate to memory accessibility, memory management, and enhanced security features. The security features that are available in the 64-bit versions of Windows  include the following:

• Kernel Patch Protection
• Support for hardware-backed Data Execution Protection (DEP)
• Mandatory driver signing
• Removal of support for 32-bit drivers
• Removal of the 16-bit subsystem

One of the greatest advantages of using a 64-bit version of Windows  is the ability to access physical memory (RAM) that is above the 4-gigabyte (GB) range. This physical memory is not addressable by 32-bit versions . 

Depending on the version of Windows  that is installed, a 64-bit version of Windows  supports from 1 GB of RAM to more than 128 GB of RAM. The ability to address more physical memory lets Windows  minimize the time that is required to swap processes in and out of physical memory. Therefore, Windows  can manage processes more efficiently. This memory management feature helps improve the overall performance of Windows .

Advantages when you install a 64-bit version of Windows 

• Increased memory support beyond that of the 4-GB addressable memory space that is available in a 32-bit operating system
• Increased program performance for programs that are written to take advantage of a 64-bit operating system
• Enhanced security features

What to consider when you install a 64-bit version of Windows 

• 64-bit device drivers may not be available for one or more devices in the computer.
• Device drivers must be digitally signed.
• 32-bit device drivers are not supported.
• 32-bit programs may not be fully compatible with a 64-bit operating system.
• It may be difficult to locate programs that are written specifically for a 64-bit operating system.
• Not all hardware devices may be compatible with a 64-bit version of Windows .

I hope that answers your questions Nikhil.