My scroll wheel works fine in Excel 2000 VBA window without any modifications.
Maybe you have wrong/obsolete mouse driver. Check your Control Panel Mouse description. It should exactly describe your hardware, not some generic driver. Download correct driver from manufacturer.
Possibly your Excel version is no longer supported by MS Update. You might need to manually download/install relevant updates since your re-install. MS provides an Office Update Inventory tool to generate a complete list of all updates, both installed and required as well as relevant and superceeded. Check out:
http://office.microsoft.com/en-us/or...402491033.aspx.