32 bit and 64 bit software
64 bit version of software (such as windows) is the newer version of software. It is faster and allows the use of larger memory. Windows 32 bit has a 4 gig memory limit, but Windows 64 bit has a limit of 128 gig memory limit (that does not mean that you can add 128. The total amount depends on the limits of other items as well such as the limits of the motherboard)
Can 64 bit software run on 32 bit hardware? No. You have to have 64 bit hardware to run 64 bit software.
Can 32 bit software run on 64 bit software? Yes it can. You will not have all the features and speed of 64 bit software though.
Is all hardware such as printers, scanners and such compatible with 64 bit? No. This is the case with 32 bit version as well. It is more widespread with 64 bit due to 64 bit is a newer version. Newer hardware in general will not have an issue with 64 bit. Check with the manufacturer for information on that individual piece of hardware. There may be an updated driver for the item.
Is there a 64 bit version of all the software available for 64 bit windows? No but more software is being designed for 64 bit. However majority of 32 bit software runs fine on 64 bit platform.
Flash and 64 bit version of Internet Explorer
Do you recommend buying 64 bit computer and 64 bit version of Windows? Yes, I haven't had any issues with 64 bit windows except for the Flash issue but there is a workaround for that.
Will a file that was created with a 64 bit software work with 32 bit software? Yes. Data has no bearing with the 32 or 64 bit. For instance, If you had 64-bit word and created a document in it. You can open it in 32-bit and vice versa. The only thing that would interfere is if one is an older version. For example, Word 2007 will read Word 2003 but Word 2003 will not read Word 2007 unless you have a converter.