I have been working all night on some word document and excel document on my mac, and I'm at work now but the files wont open, I have Mac office 2007 at home and office 2003 on this XP machine
Office 2007 for Windows and 2008 for Mac at completely compatible when using the new 'x' formats of Office documents. (e.g. .docx, .pptx, .xlsx)
When using older versions of Office you need to make sure you save them in the compatible Office 97/2003 formats that don't have a 'x' suffix. (e.g. .doc, .ppt, .xls)
It's not a problem at all.
In fact, go into word preferences and set the save default to the earlier version and you won't have to worry about it anymore.