Guys,
For info., you can always partition the Hard Drive on your P.C. (with a prog. called Partition Magic) so you can set up 2 or more Operating Systems on that machine. You get a choice of which Op. System you want to use when you Boot-up, so you can retain your old system and install a later version(s) as well if you want.
This feature was especially useful in the case of Excel Spreadsheet, where earlier versions which ran on Win95 had a much simpler to understand Macro recording and writing system (the code being almost in plain English), rather than the current Excel which uses Visual Basic for Macros.
Hope that helps.