To do a case-insensitive search for node names with XPath, use something like this:

"//form[translate(., 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz')]"

This example searches for FORM tags inside an XML document. The dot ‚.‘ here means that it applies to the tag name.

Therefore the above would match e.g. „form“, „FORM“, „Form“ or „fOrm“.

The Microsoft Knowledge Base article „INFO: Use XPath to Perform a Case-Insensitive Search with MSXML“ helped me to find out.