.exe programs not opening due to virus

[maddierose]

hey guys, for a while now, I have been having a strange problem which im sure is virus related. When I log in, I get windows popups, due to .exe programs being unable to run. They come up with different headings, yet the actual notifications inside are all the same. The headings are:
HPAdvisor.exe - Configuration parser error
HPWAMain.exe - Configuration parser error

When I try to open The Sims 3 which I have tried to install from the original disk which used to work fine I get this:
Sims3Launcher.exe - Configuration parser error

I tried to install Facebook Messenger last night, when I try to run it I get:
FacebookMessenger.exe - configuration parser error

Inside all of those notifications is this same message:
C:\Windows\Microsoft.NET\Framework\v2.0.50727\config\machine.config
Parser returned error 0xC00CE556

For antivirus I use Avira Free Antivirus, I have done a full scan which has detected nothing. But I am unable to update it, when I click "Start Update" I get a notification saying
The following error occured when trying to start the update:
Access denied..

I am hopeless with this kind of stuff, how can I get my computer back to normal? Thank you

[SuperDave]

Hello and welcome to Computer Hope Forum. My name is Dave. I will be helping you out with your particular problem on your computer.

1. I will be working on your Malware issues. This may or may not solve other issues you have with your machine.
2. The fixes are specific to your problem and should only be used for this issue on this machine.
3. If you don't know or understand something, please don't hesitate to ask.
4. Please DO NOT run any other tools or scans while I am helping you.
5. It is important that you reply to this thread. Do not start a new topic.
6. Your security programs may give warnings for some of the tools I will ask you to use. Be assured, any links I give are safe.
7. Absence of symptoms does not mean that everything is clear.

If you can't access the internet with your infected computer you will have to download and transfer any programs to the computer you're using now and transfer them to the infected computer with a CD-RW or a USB storage device. I prefer a CD because a storage device can get infected. If you use a storage device hold the shift key down while inserting the USB storage device for about 10 secs. You will also have to transfer the logs you receive back to the good computer using the same method until we can get the computer back on-line.
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You can find more information about this problem here.