To repeat what Joe mentioned:
"The free version should be able to handle all detected malware the same as the paid version."

The only time it would not be able to handle what it finds would be if the files are running. (In that case you would run your scan in Safemode.)

The only features that you lose when the trial runs out are the realtime Guard, and automatic updating. As long as you are updating manually, there should be no problem.

Exactly what is your AVG AS finding that it cannot clean or quarantine?

Virtumonde has many variants and often brings other malware with it, so it's probably regenerating the nasty stuff. The general scanners don't catch all of it.

It probably would be good if we could see what is running around in there, so I'm going to send you for a diagnostic tool. After you run it and post on the HijackThis board we will know more.
** There is a list of trained analysts at the top of that board in the Announcements. If someone else replies, it will be your decision whether or not you want to take advice from them.

Click HERE OR HERE to download HJTsetup.exe

1. Save HJTsetup.exe to your desktop.
2. Open Notepad > Click on Format > Uncheck Word Wrap, if checked.
3. Double-click on the desktop icon for HJTsetup.exe and by default it will automatically install to C:\Program Files\HijackThis.
4. Continue to click Next to accept the default settings in the setup dialogue boxes until you get to the "Select Additional Tasks" dialogue.
5. Put a check by Create a desktop icon then click Next and continue accepting the default suggestions.
6. At the final dialogue box click Finish and HijackThis (HJT) will launch.
7. Click on the " Do a system scan and save a logfile" button"; A log showing the results should open in Notepad.
8. Click on Edit > Select All (or CTRL+A) then click on Edit > Copy (or CTRL+C) to copy the contents of the log.

Posting Your Log:

1. Next, just click the New Message button in the HijackThis forum
here: http://www.dellcommunity.com/supportforums/board?board.id=si_hijack
to start your own thread requesting assistance.
2. In the Message Body window that opens, simply Right-Click and select Paste.
3. Please add text to describe your symptoms.
4. Include in the message subject line a description of your problem. For example, "Popups warning of infection".
5. Make certain you post the entire log by clicking the Preview Post link at the bottom of the window and comparing it to the log from your scan before you click Submit Post

** Note: "The box next to Automatically convert carriage returns to HTML line breaks" should be checked if that appears at the bottom of your Message Body when composing your post.


NOTE:
* DO NOT have Hijack This fix anything yet. Most of what it finds will be harmless or required.