The first 64-bit computer that was introduced is the IBM 7030 aka "Stretch", which was shown in Los Alamos, New Mexico 1961. Most 64-Bit Windows computer may not have the backwards compability to many 32-bit/Win32 applications.
IBM 7030 Stretch
http://en.wikipedia.org/wiki/File:IBM7030_p1040280.jpg
Most 64-bit processors can be found on supercomputers, professional servers and on latest desktop PCs. Unlike most 32-bit Windows PCs, the 64-bit PCs can engage more RAM than 32-bit PCs as they can only use no more than 4GB RAM.
AMD Athlon 64 X2
http://cdn.cpu-world.com/CPUs/K8/L_A
During the 32-bit era near the mid 1990s' most computers or game consoles were introduced and used the CD-ROM media technology. However the Nintendo 64 is unique as it uses the 64-Bit MIPS NEC chipset and didn't use the CD-ROM drive. The Atari Jaguar was also another type of early 64-bit console that is similar to the Nintendo 64 but failed to compete as the Jaguar was a commerical failure.
