[Need help with removing 2 trojan agents]

Hi

Im having a lot of trouble removing 2 specific trojan.agents from a customers desktop pc. Have ran Malwarebytes and removed them but then doing another scan it picks them up again.

The 2 that keep coming back our:

Trojan.Agent: HKLM\System\Currentcontrolset\Enum\root\legacy_microsoft_windows_service

Trojan.Agent: HKLM\System\Currentcontrolset\Services\Microsoft windows service

I have tried using programs such as TDSS KILLER, Combo-fix, Rkill, Roguekiller but im having no luck with any of them. The internet is working but trying to get to a security site such as AVG brings up "internet explorer cannot display the webpage"

Im also getting the following 3 infections which wont remove either:

PUM. Disabled.SecurityCentre: HKLM\Software\Microsoft\SecurityCentre\Antivirusdisablenotify

PUM. Disabled.SecurityCentre: HKLM\Software\Microsoft\SecurityCentre\Firewalldisablenotify

PUM. Disabled.SecurityCentre: HKLM\Software|Microsoft\SecurityCentre\Updatedisablenotify

Has anyone seen these infections before and got round them? would appreciate any help