See this link.
Error 651 with PPPoE connections in Windows 7 | Windows Reference
Again, you are not alone, this seems to be a
known bug in Windows 7 that is being worked at.
However, you can workaround this problem.
The RAS PPPoE driver file “raspppoe.sys” found under
c:windowssystem32drivers folder seems to be the
root cause of the problem. Fortunately, we can
workaround the problem simply by renaming the
original raspppoe.sys file to something like
“raspppoe_orig.sys” copying a working file from a
Windows Vista system. If you do not have access to a
Windows Vista system. click here to download
raspppoe.sys file (unzip).