Hi Coatond, and welcome to the forum.
1. Are your file types (.xlsx, .xlsm, etc.) configured in Explorer correctly? Perhaps there is also an issue in the registry (see here: http://support.microsoft.com/kb/323216)
2 & 3. Somehow your context menus must have been turned off (via macro?). To re-enable the right-click menus for the sheet tabs and cells, copy and paste the following code into the VB Editor and run each macro. Close the VB Editor and you should be able to right-click on those areas again.
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