Changing Win XP to 7

[Raiyushi]

The difference between 64-bit and 32-bit is amount of data they can address at once...

64-bit operating systems can address 64-bits worth of data.
32-bit operating systems can address 32-bits worth of data.

What's this mean?
32-bits of Data can only address 32-bits of data at once which is about 4GB.
However, due to overhead you can expect to address about 3.3GB. So if you have MORE than say...3.3GB of memory you'd want to go for a 64-bit operating system, but if you have LESS than that amount it really doesn't matter.

Some applications are designed to run in 64-bit operating systems, meaning they're designed to be able to use more than 4GB of memory. This is usually not the case with almost all applications, and most applications that are 64-bit will run just fine even if you're not running a 64-bit operating system. The only applications I can think of that would use more than 4GB of memory would be something like a really badass photoshop, or Autocad/3D Design applications/etc.

Also, you CANNOT upgrade from XP -> 7. It has to be Vista -> 7 so you will HAVE to make a backup of what you want to keep.

---