The components of Microsoft Office XP are all '2002' products. (e.g. Word 2002, Excel 2002, etc) yet, strangely, neither 'XP' or '2002' products are even listed here:
http://www.microsoft....es&v=Microsoft&page=1
That link is the first of 9 pages, detailing which Microsoft programs are immediately compatible with Windows 7, which require a (paid) upgrade and which won't work at all. However I do note that the '2000' products require a paid upgrade in order to get them to run under Windows 7, so that might well be the cause of your problem.
Your simplest solution might be to ditch Microsoft Office in favour of Open Office. It's free and (unless you use things like extremely complex macros) compatible with Microsoft Office:
http://www.openoffice.org/
Chris