Differents between windows 32-bit vs. 64-bit systems

• Allows individual processes to address more than 4 GB of RAM each (in practice, most but not all 32-bit OSes also limit the total usable system RAM to less than 4 GB, not just the per-application maximum). Get keys for win 7 64 bit ,win 8 64 bit ,with lower price ,welcome to my store :http://www.mskeyoffer.com/
• All pointers take 8 bytes instead of 4 bytes. The effect on RAM usage is minimal (because you're not likely to have an application filled with gigabytes of pointers), but in the worst theoretical case, this can make the CPU cache be able to hold 1/2 as many pointers.
• There are many more general-purpose CPU registers in 64-bit mode. Registers are the fastest memory in your entire system. There are only 8 in 32-bit mode and 16 general purpose registers in 64-bit mode. In scientific computing applications I've written, I've seen up to a 30% performance boost by recompiling in 64-bit mode (my application could really use the extra registers).
• Most 32-bit OSes really only let individual applications use 2 GB of RAM, even if you have 4 GB installed. This is because the other 2 GB of address space is reserved for sharing data between applications, with the OS, and for communicating with drivers.  A 64-bit OS can give individual 32-bit applications closer to the full 4 GB to play with.

• Application speed is usually faster for a 64-bit application in a 64-bit OS compared to the 32-bit version of the application on a 32-bit OS, but most users won't see this speed-up. 
• If you have any memory hog applications (like photo editors, video processing, scientific computing, etc.), if you have (or can buy) more than 3 GB of RAM, and you can get a 64-bit version of the application, the choice is easy: use the 64-bit OS.
• Some hardware doesn't have 64-bit drivers. Check your motherboard, all plug-in cards, and all USB devices before making the switch.
• If you run so many applications at a time that you're running out of RAM (usually you can tell this because your computer starts getting really slow and you hear the hard disk drive crunching), then you'll want a 64-bit OS (and sufficient RAM).
• You can run 32-bit applications (but not drivers) in 64-bit Windows with no problems.