Hi All (Been a while)

I have been given a bit of an epic job.
I have an enormous code base. Literally hundreds of folders with thousands of VB.net and VB solutions scattered around.
My job is to search through all the code and identify where the code in some way hits the local drive. Any code that for example alters a registery key or reads a file from current applicationpath/sub folder.
I will use some kind of grep tool or will write one myself.

What the heck should I search for? There are so many ways to mess around with the client machine.

All comments welcome. Thanks in Advance :-)