Cannot download, false virus read on everything

using windows 7 home premium.
ive ran malwarebytes, roguekiller, and hitmanpro.
used uninstall tools for all antivirus programs previously uninstalled.
currently using Microsoft essentials.
I've tried everything.
renameing windows defender is the only that will allow downloads.but I know that is not a permanent fix and the problem still persists.

so frustrated!