How to replace the Existing XSL tag in an XML file in C#( using any of Files/Streams/Regex/Strings)

Question

Hi,
While working for one of my tasks I have encountered this Problem.

Problem: I have an XML file which contains an like this

<?xml-stylesheet type="text/xsl" href="OldStyle.xsl"?>

and I want to remove this tag and Replace it with a new like this:

<?xml-stylesheet type="text/xsl" href="NewStyle.xsl"?>

The replacement should be done for a no.of files and I am supposed to do this task using C# with .NET 2.0 (without using Linq).

I have tried by Googling and going through various blogs Yet could not find the right solution. Any help is appreciated.