option 1.
vagrant plugin list
vagrant plugin uninstall <name of the plugin>
Option 2.
http://answers.microsoft.com/en-us/windows/forum/windows_7-files/windows7-will-not-let-me-edit-the-hosts-file-and/9cede7a3-1908-4606-a955-64a9b4872fd7?page=2&auth=1
JaeSmith replied on
It also helps if you can follow the path to: C://Windows/System32/drivers/etc
Find the host file and right click "Properties" the select "Security" tab.
Select the Group or Username that has full control privileges on your
machine. There should be a list of users in the box.
Click on "Advanced" button and select from the "Permissions entries"
the administrator that has full control privileges and then select the
"Owner" tab. Select the "edit" button and then choose the owner to
take control of that file.
Click "ok." Next, from the same box, choose "Effective Permissions"
tab and then click "Select." Go to the "Advance" button and then click
"Find now" button. Select the administrator in the search results box
that you want to give full control to if administrator doesn't have it
as indicated by all the check marks.
Click "ok." If the check marks are not automatically populated then
making sure that you have selected the administrator that you want to
give full control privileges to under the "security" tab, manually
check ( or click to add check marks) all full control and writes
privileges for that administrator. Make sure you go to the "edit" box
in order to make these revisions.
>
https://groups.google.com/d/msgid/vagrant-up/bd09252a-7f62-447c-b0ff-45ba3e4ce7b4%40googlegroups.com.