TrojanDownloader:Win32/Dofoil.O virus found, cleaned, deleted, still have issue's HELP

Recently I was hit with 3 viruses. MSE caught them but one kept coming back. I let Microsoft support take over my computer and after they finished they assured me it was clean. I later found a file on my desktop and I didn't put it there. I deleted it, the short cut and the location it pointed to. I checked my event logs and founf the following entry

Microsoft Antimalware has detected malware or other potentially unwanted software.

For more information please see the following:

http://go.microsoft.com/fwlink/?linkid=37020&name=TrojanDownloader:Win32/Dofoil.O&threatid=2147653354

Name: TrojanDownloader:Win32/Dofoil.O

ID: 2147653354

Severity: Severe

Category: Trojan Downloader

Path: containerfile:_C:\Documents and Settings\Dell\Application Data\A6AF17.exefile:_C:\Documents and Settings\Dell\Application Data\A6AF17.exe->(UPX)regkey:_HKCU@S-1-5-21-1390067357-1767777339-1801674531-1003\SOFTWARE\MICROSOFT\WINDOWS\CURRENTVERSION\POLICIES\EXPLORER\RUN\\Pure Networksrunkey:_HKCU@S-1-5-21-1390067357-1767777339-1801674531-1003\SOFTWARE\MICROSOFT\WINDOWS\CURRENTVERSION\POLICIES\EXPLORER\RUN\\Pure Networks

Detection Origin: Local machine

Detection Type: Concrete

Detection Source: System

User: NT AUTHORITY\NETWORK SERVICE

Process Name: Unknown

Signature Version: AV: 1.121.908.0, AS: 1.121.908.0, NIS: 0.0.0.0

Engine Version: AM: 1.1.8101.0, NIS: 0.0.0.0

After seeing this I went into the registry and did a search for S-1-5-21-1390067357-1767777339-1801674531-1003 which is part of the above path. There are many entries in the registry. I'm familiar with the registry and editing it. However, I do not make modifications to it unless I know for a fact what I'm doing. Do I need to remove these entries from the registry? In my research I also found in Local Security Settings > Local Policies > User Rights Assignments several entries of the same string under the Security Setting column. Do I need to do any thing with these entries?

Any help will be greatly appreciated.

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