RE: Pre-installed software doesn't recognize compatible document.
You should have received a recovery disk with your computer. Normally,
such problems can be taken care of by recovering using only reinstall the
software. This won't lose your documents and other personal information,
but may cause some difficulty with some of the programs you've installed
since you first got the computer. Any that show problems should be
reinstalled.
If that doesn't work on your microsoft files (my documents), you need to use the the recovery disk to format the hard drive and reinstall your original software.
As a warning, before you do that, you need to save a number of files(hopefully to a zip disk if you have one) or to floppies . Among them are your bookmarks, address book, software downloads such as the unzip file, adobe, etc, important email and the personal files you keep any finances on, letters, spreadsheets, wordprocessing documents, etc. Take your time developing a list of what you have that you want to keep.
It takes some guts to do as chances are you will have forgotten something, but your computer will run "as good as new" and you will be able to open your files.