This VBScript code tells you if Excel is running, and makes the first instance it finds visible.
Copy this code into a text file, and save it in a convenient folder or on your desktop with a name like 'XLcheck.vbs'. When you think you've left an invisible instance of Excel running, run this (by double clicking) to make it visible, so you can deal with it.
' XLcheck.vbs
' Find an invisible instance of Excel
' from Rob Bruce
Dim objXL, strMessage
On Error Resume Next
' Try to grab a running instance of Excel:
Set objXL = GetObject(, "Excel.Application")
' What have we found?
If Not TypeName(objXL) = "Empty" Then
strMessage = "Excel Running."
Else
strMessage = "Excel Not Running."
End If
' Feedback to user...
MsgBox strMessage, vbInformation, "Excel Status"
' Make it show so we can kill it
if strMessage = "Excel Running." then objXL.Visible = true
' End of VBS code
[Via]