.xll add-in Error in Windows XP "Not a valid add-in"

[Alice]

I'm trying to include an Add-in into Excel 2000 in Windows XP operating
system. This .xl add-in works perfectly in Windows NT, but then when I'm
trying to add the same .xll add-in in Windows XP excel, I get the following
error.
"This is not a valid add-in"

Is there a workaround to it? The source code for this .xll add-in is
password protected and I do not have the rights to alternate or make any
changes to it.

Thanks.

 

[Jens Thiel]

Your add-in may depend on one or more DLLs not available on XP / your
specific XP setup.

Jens.