Windows Vista will only run Microsoft Office 2003 or Microsoft Office 2007. It will not run Microsoft Office XP because it was designed for a 32 bit architecture on Windows XP. The copy of Vista Business I have on the computer in my signature has Microsoft Office 2003 on it, and it was upgraded to Microsoft Office 2007 this morning. Install them, and if they don't work, you might as well try downloading updates from the Microsoft website.
You might want to download a trial of Office 2003/2007, or you might want to order a trial CD which is absolutely free, but can take between 3 and 5 working days to get delivered, although the download is about 700Mb. I think it is in executable and ISO format, from external sources, but only as a trial CD from the Microsoft site, the only site I can guarantee where the download is legal.