Mixing include path styles. How do I do this???

We recently switched from Netscape Enterprise to IIS and I now need to make a lot of changes to over 600 htmls - mostly in include statements. We're doing two things here, switching servers and switching all our SSI's to PHP includes. Under Enterprise, I could define a path just by putting it into the include from the root, ie: <!--#include virtual="/acc/includes/headstart.htm"--> I used a global Find and Replace app to change all these (each html has about eight includes) to: <? include '/acc/includes/headstart.htm'; ?> and now they don't work. If I replace the whole path with a Windows path structure (C:\...) to the included file, it does work. Here's the problem as I see it. I can easily do another Find and Replace to add in the first part of the directory tree to the web directory. What I cannot easily do is change the "/" to "\" inside the path for the part of the path that's already there. Is there some way to define the path to the web directory using "\", maybe in a variable and then somehow/way switch over to "/" so I don't have to mess with the paths I already have? Or maybe there's a solution I'm not even aware of. Thank you.