Try this:
Go to Control Panel > Administrative Tools > Computer Management > Local Users and Groups > Users
Find your username and double-click it.
Click on the member of tab and then if it doesn't say "Administrators" go to <Add> then type "Administrators and <OK>
Then try installing the app again. The changes should be instant and no restart should be required.
Hope this helps
EDIT: Actually if you aren't a member of the admin group you won't be able to add yourself as one. If you restart in safe mode you should be able to log in as either your own account or one called "Administrator", created by windows when you ran setup. Log on as that then complete the steps above and restart.