Data Missing in Excel & Word files

I have Office 2003 Basic with XP. All my files=20
(excel,word,pdf,mp3's etc) has suddenly lost their data=20
and instaed have gibberish inside the files (like=20
charaters etc) Dell support staff have been the least=20
been helpful . Have tried repair console, repair=20
installation. But no avail. I have checked for trojan or=20
virus with 3 different checkers ( Norton, McAffee etc)=20
Nothing. Whenever I tried to open a excel file, I would=20
get a text import wizard box, and instead of numbers it=20
would characters like =C7 , =C8 or etc. Any new files I=20
have made and saved are ok. This is only happened on my=20
old saved files. One particular funny thing all my=20
Peachtree Accounting files are ok.=20
Please Help.
P.S: Being the GeniAss, I had shut off the system restore=20
couple of days before I had the problem.