64 or 32 although the 64 will be able to run 32 bit programs.
Installing Linux on a 64-bit processor is no different than installing it on a 32-bit processor. Especially on systems that offer both a 32-bit and 64-bit version, the difference is totally transparent, and the install identical.
Yes. Google offers both 32-bit and 64-bit binaries for Linux on Google Earth's download page.
an ios CD to do CD boot probably 32 bit for laptop and 64 bit for desktop but check in on that
The same as any OS - up to 4GB for 32-bit systems, and 16EB for 64-bit systems.
Yes, as long as the operating system provides 32-bit libraries. 64-bit editions of XP and Vista provide these by default. Most Linux distributions do not (since most of their programs are free and can be compiled to 64-bit anyway), but will offer the libraries in their repository.
Yes. x86-64 processors are capable of using both 32-bit and 64-bit operating systems and programs. Note that if you are using a 64-bit operating system, the system itself must be capable of running 32-bit binaries as well. Windows XP Professional x64 and 64-bit versions of Vista include this functionality. On Linux, since almost all programs come in a 64-bit version anyway, you have to install 32-bit libraries to run them.
i686 is a designation for an Intel processor architecture, falling under the x86 family. It's a 32-bit architecture. Kernel builds and distributions targeted for the i686 are for 32-bit processors/systems.
If you are using Linux then you can use uname command, which prints system information including kernel version and whether kernel is 32 bit or 64 bit. You can also use less /proc/cpuinfo command determine if it is 64 bit CPU or not. Example: $ uname -a
Usually, yes. Windows XP Professional x64, Windows Vista x64, and most Linux distributions all offer the ability to run 32-bit programs transparently on top of a 64-bit system. If your CAD program is compatible with the 32-bit edition, there is a very good chance that it will run without any problems on the 64-bit edition.
There are different versions of Vista as well as 32-bit and 64-bit for each. To switch from 32-bit to 64-bit you would have to make sure that you have 64-bit compatible hardware and would have to purchase a 64-bit version of Vista.
A 32 bit processor has 32 bit wide data bus while a 64 bit has 64 bit wide data bus. Address bus may or may not be 32 bit or 64 bit wide in the respective processors. To fully utilise the 64 bit data bus the programs must be written in such a way that they can use 64 bit wide data bus. A 64 bit processor can also act as 32 bit.
You mean 32-bit and 64-bit, not 32 byte and 64 byte. A byte is an aggregate of (usually) 8 bits. 32-bit programs will execute in a 64-bit environment without any modification. 64-bit programs can also execute in a 32-bit environment, but this requires emulation through a 64-bit virtual machine.