32 bit compilers

I have some legacy 32 bit Fortran compilers which I use and work great on XP. I have also tried the compilers on a Vista machine (32bit?) and they work fine. I would like to upgrade to a Windows 7 machine. I have tried my compiler on a Windows 7 home edition desktop and it does not work on the dos window.
My question is can I install a 32 bit version of Windows on a new machine or do I have to upgrade home to to Windows professional and get a new 64 bit version of a Fortran Compiler?

Can I buy a new portable/desktop and specify a 32 bit version of the operating system?
And will this work with my 32 bit compilers?

Windows 7 Professional and Ultimate comes with a XP mode. If for some reason Fortran does not work in a standard install. You should be able to get Fortran working in the XP mode. However I do not have any experience with XP mode or Fortran and cannot tell you for sure it will.

Two articles you might find of interest

Windows XP Mode

Most 32-Bit Applications will work in 64-Bit Windows. It hardware drivers that must be 64-Bit to install.

Windows 7: 64 bit vs 32 bit?