MakePath resolves “C:” correctly, and shows same output for "C:". There’s a difference though for Volume D, as shown in the screenshot. The node would resolve the path to the running vvvv instance’s folder. Thats’s probably because vvvv is running from Volume D (so probably it shows the same behaviour for C if vvvv is running from there), but it shouldn’t be that way nontheless.
On a second note, the node holds the last valid output if a pin is turning nil.
It should probably either handle it as an empty string or output nil.