How to resolve the error while opening an excel workbook?

It means that, for some reason, when you execute your code, the xls file is not found in the directory you're looking in.  Double check to make sure that, on the machine on which you're executing the code there is a D drive with a test1.xls in the root.

Also... make sure that non-admin users have access to that root.  You might need to run TestComplete as an administrator to get access to D root.