I have used Delphi 7 for many years, but having bought a new machine with Windows Vista, I get lots of error messages and warnings and it is unstable in operation.
Alec Wiliams
Delphi 7 is rather old so you might consider upgrading. However, someone asked the same question at the excellent Stack Overflow site, and the answer is that "Delphi 7 under Vista is no problem if you can turn UAC [User Account Control] off." Dr Bob also has a useful article about running Delphi on Windows Vista.