Were these pictures taken with the iPad and did you import them using the W7 Import Wizard? If so it should have asked you where to put them. If you don't recall try this:
Open Windows Explorer. On the left side folder structure, select Libraries, then go to the upper right corner and look for the "Search Computer" box.
Type exactly img*.jpg and then click Enter. This will bring up all pictures taken with the iPad (and likely others) that are under your user libraries.
If you still cannot find them, then open Explorer again but this time select Computer, then go to the upper right corner, "Search Computer" box.
Type exactly *.jpg and then click Enter. This will bring up all pictures taken with any camera in the JPEG format. This search will take some time.
If this does not find them, they are not there.