Excel 2000 No open close dialog box

When attemption to open a worksheet from the menu bar. File Open: no dialog box displays. You have to go into MS Explorer and launch the program by clicking on the worksheet. Also, when saving a worksheet NO dialog box appears for save as. You can not look at the properties of the worksheet either. This machine suffered drom Nimda and has been cleaned and the Office software re-installed, uninstalled and re-installed and repaired numerous times and upgraded to Service Pk 2 for Office 2000. Inother words you can only open the documents by clicking on them via explorer, but you cannot save as. If you just you just click on save it does ask if you want to replace the original but you cannot do SAVE AS:
Any idea would be greatly appreciated.