Yes...
link is attached !
Yes... link is attached !
Dual-boot or multiboot.
"Distros", or distributions.
Distributions
There is no such thing as "Linux XP". If you're referring to Windows XP, then the answer is no. As far as Linux distributions, for the majority of distributions, they are free (as in freedom) and free-of-charge.
Dos Linux Windows 95 Windows 2000
Many distributions have older disk images in their archives. Try there.
It's not just in Linux distributions. AMD64 is the "friendlier" term for the 64-bit x86 architecture (x86_64 or "64-bit Intel" as a lot of people like to call it.) What this means in the context of Linux is that distribution is available for 64-bit PCs. This is akin to Microsoft labeling certain versions of Windows as being "64-bit." It should also be noted Linux came to x86_64 long before Windows did and arguably uses long mode in so many better ways than Windows (Including the fact Linux has far more of a selection of 64-bit software than Windows.).
Linux is free. However, this question can be taken at an angle of total cost of ownership or time cost investment. Since specific versions or distributions are not specified this cannot be answered. Some RedHat versions can be more expensive than some Windows versions. Linux sometimes takes more time to maintain than Windows, so overall it can switch license costs into time costs. If Windows systems take fewer employees to run, then the higher initial license costs can be viewed as necessary and Windows as "less expensive" over time. For a private party on a personal computer, Linux like Ubuntu, can be less expensive to install and operate.
Windows costs money, but Ubuntu is Linux-based and free. Ubuntu is one of many distributions, or versions, of Linux. Personally, I like Linux better than Windows but Windows programs can't run natively on Linux (and vice versa) so many Linux users still use windows because they need to run certain programs. Compatibility/"emulation" (in quotes because it isn't true emulation) is available in the form of the Linux program WINE (stands for WINE Is Not an Emulator). Linux, in general, is not intended for those who are not experienced with computers, and the sterotypical Linux users are computer programmers. However, several more recent distributions have broken this mold, including Ubuntu. Ubuntu is a very user-friendly distribution, and an excellent place for someone curious about starting with Linux to start. Personally, I prefer the distribution openSuSe, but it requires a slightly higher experience level with Linux to use effectively.
Linux is not an operating system by itself. Just like you cannot install Windows you have to install Windows XP or Windows Vista. You can use the website in related links to find a list of active Linux Distributions. If I could recommend one I would recommend Linux Mint because it is easy to use.
Generally speaking, no. Windows has a slower patch cycle than most Linux distributions, thus exploits are exposed for longer and have a greater probability of being hit.