Finding values in an XML File

HI.

We get files sent to us from 3rd partys. All of these files are XML and contain a unique number.
However we cannot find them using windows search.

I think it's due to the fact that these are XML Files.

For example, one file has a line

<OUTBOUND_NO>0800000003</OUTBOUND_NO>


now, If I do a windows search on the folder containg this file for 800000003, it will not find it.
And I'm using the "any Phrase in File" option on the search.

Is there any way I can find these files easily.

The Number I need is not in the file name, and I can;t search each one individually.

Is there a parse search program I can use or something like that?

Thanks
dave