compatibility of office 2007 with old version and mac version offi

Recently I installed office 2007 on my pc, windows xp. When I tried to open
an email attached old version excel files (from a mac user), the office 2007
could not be pumped up, instead, the windows installer wanted to install the
old version office which had been uninstalled by the installation of office
2007. So I had to open 2007 excel program first and then find the file and
open it (incompatible with mac version?). In order to avoid the conflict
between the old version and office 2007, I thought it would be better to
completely remove the old version. So I clicked contral panel "add or remove
program" . On the program list, i found the old version office xp still
there. but when I clicked the remove button, i was told "this patch package
could not be opened." (how can i completely remove the old version office xp?)
Thanks,