How did you upload the files? Did you make a local folder a Live Mesh folder and then place files into the local folder, letting Live Mesh upload them to the Live Desktop? If so, the files may not have fully uploaded and you are clicking on incomplete files or placeholders on the Live Desktop.
If you uploaded the files from your PC to the Live Desktop directly, but then cannot open them, try resetting your IE to default as a setting may be blocking the ability to view the files. The Excel file should prompt you to download or open the file. If you select open, it downloads and launches Excel. To reset IE, go to Tools/Internet Options/Advanced.
-steve
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