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I'm looking to build a new computer and was wondering what the difference is in 32 vs 64 bit Windows Seven. I do know that 64 bit allows for more RAM.

Also, will old programs run on a 64 bit machine? For example will World of Warcraft etc run on a 64 bit copy of Windows Seven?

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Microsoft's website has an article covering the differences in more detail.


Programs written without explicit 64 bit support should work on 64 bit Windows, since programs in the Program Files (x86) directory are emulated. If you want to know beforehand whether an old version of a program works in 64 bit Windows, you could look at the system requirements page in the Wayback Machine.

Since Windows 7 at both 32 bit and 64 bit are sold together, you can always reinstall with 32 bit Windows if it turns out a program you really need only works on the 32 bit version.

1 Some CPUs support this feature in 32 bit windows through PAE (as said by grawity).

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fwiw, many CPUs support hardware DEP and big RAM even in 32-bit mode -- through PAE. – grawity Jul 31 '10 at 22:13
CPUs may support more RAM in 32 bit mode, but Windows 7 doesn't. Only way to get mroe than ~3.5 GB of memory in Win7 is to use 64 bit. – Jason Berg Jul 31 '10 at 23:43
Windows 7 64 bit has a nice feature for program compatibility called XP Mode. Basically installs a free copy of XP on a virtual machine. You can also install a lot of 32 bit software in a 64 bit environment. Support for 64 bit has really moved forward, I wouldn't be afraid about taking the jump, plus as @Simon Brown pointed out, both 32 bit and 64 bit come together in same box. – ubiquibacon Aug 1 '10 at 1:52
@James Watt, my story is about the same. Vista took a lot of the punishment related to the growing pains of a 64 bit OS, the result is an excellent OS in Windows 7. – ubiquibacon Aug 1 '10 at 5:47
Always use 64-bit version. 32-bit generation is already over. In often, machines running Windows 7 carry >4GB RAM. Therefore, 64-bit W7 is needed. – Raptor Aug 1 '10 at 8:51

World of warcraft will run fine on win7 x64. As will 99% of software that supports XP (common software anyways). Anything not x64 will be emulated.

There isn't that much that will not run on x64 except some older drivers. But if those drivers don't support x64 chances are they don't support Vista or Win 7 anyways. Software problems on Win7 is very rare and at worst you may have to use compatability modes.

I would go with x64, there are very few reason not to.

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