Win32:Trojan-gen when do Boot sector scan

Hi guys
First post here
Hope you would bear with me

When I did a scan of the boot sector using AVAST 5, I found that I had 2 files that appears to be infected by the Win32:Trojan-gen virus

It also seems that a system volume info is also affected by the same virus

Attempts to Press 1 to delete was in vain as it returned the error code 42111

I am also unable to move to chest or to repair it

However, when I try to scan for it under windows, AVAST 5 returned negative for virus. I also scanned with A Squared, ESET which all showed negative for virus

My question is whether I should be worried? How do I removed the Win32: Trojan-gen virus from the boot sector?

Whas there a log?
Where was the infection found?

The strange thing is I cannot find the AVAST log file
During the boot sector scan, they indicated the path where the log file can be found right? But when I tried to look for that folder, it cannot be located
And when I search for the files under file search in Windows, I cannot find the supposed infected files as well
I am puzzled, if this a false alarm?
How do I proceed from here?
Thank you

Okie a little more info
From the scan log inside AVAST 5 itself

The 2 affected files are
c:\Program Files\Common Files\WindowsLiveInstaller\Temp\JobData_32_00526DC8.dlt[>Product.cab]>WLXQuicktimeControlHost.exe
The other file is a WLXVideoCameraAutoPlayManager.exe

Both files says Error:The operation is not supported for this type of archive(42111)

Another 2 infected files are under c:\system volume information\ …
Which I have successfully move to the chest

How should I proceed
Many thanks to all forumers again

Latest update
Now when I do a boot scan, everything is fine
Very strange! But what a relief!
But anyone has any idea what I did rite??