For the past eight years I've used an older version of Csound (4.19 from 2005) that only runs on Windows XP. I moved to a new version of Windows, and the old version stopped running. So I obtained a current version, Csound version (5.17.11 from May 2012). To my delight it worked with all my old opcodes with only minor problems with the install. This version of the piece was made with the Windows 7 version of Csound 5.17.11.
My preprocessor, written in Turbo Pascal (filedate 1989), is another story. Turbo Pascal won't work in the current version of Windows 7. I had to create a virtual machine running XP, and that is working, but poorly. All things considered, my $90 investment in Turbo Pascal was worth it, since I have been able to use it for 23 years.
My next task is to try to port the Turbo Pascal to Free Pascal. My first attempts resulted in code that compiles with minor changes, but fails at run time reporting memory issues. That conversion will take much longer.